Displays for Small Tables

Frequently small or busy craft fairs provide a relatively a small space or table to display your glass.  This means you need to make an impact with little area in which to do it.

There is also guidance elsewhere, but these are some basic ideas to get you started thinking about how to use the space you have and make your presentation stand out.

credit: CountryHeartandHome

Make your display like a shop window display

Think about how a shop with small windows works to display things to attract your attention.  Use your stand to display a single theme or style (sometimes called a brand).  Present your key pieces in a complementary but muted background.  Co-ordinate colour, or shape, or function.  Do not put everything out at once.  Give each of your glass pieces space.  Keep extra stock behind or under the table to meet the need for different colours, sizes or shapes.  Give your pieces space to be appreciated individually. The more unity you can give to your display, the more chance you will get the attention your glass deserves.

Be imaginative in your use of display materials

Think about props you have around the studio or in your home that can complement your glass.  Look for things that fit your style of work, or the theme you are presenting.  It is the unusual, but complementary coverings and props that can help you stand out from the other displays.

Height provides interest and space

You might consider a self-supporting stand that can be placed on the table and provide shelves for your glass – as long as they are stable.  You can drape appropriately sized boxes that you brought the stock in to give height to the display.  If the boxes are appropriate, you can use them bare as platforms or shelves, depending on the arrangement.  Always think about ways to build higher, but secure, displays for your glass.  After all glass looks best with light coming through rather than flat on a table.

credit: dizziebhooked.wordpress.com

Make your display fit the glass you make

Think about what is needed to show your glass off to its best.  Mostly this will be vertical with light filtering through.  Vertical light behind or in front of the glass is good.  This is to avoid dazzling the visitor rather than displaying the glass.  It may be that jewellery is best flat, although earrings can be stunning with light behind.  You can consider constructing something that does not need a table.  Look for inspiration at the kinds of displays used by retailers to save space.

credit: pinterest

Create the illusion of space

Use light colours for table coverings and display materials.  It gives a sense of space, that black does not. Using the same colour throughout gives a sense of unity in the display.

Tablecloths are most often used because they are easy to transport, but they are not the only portable material to use.  You could consider rolls of paper, foam board, and other materials to give a clean minimalist base for the display.

What more could be done with that space behind?
credit: MacrameUK

Space behind your stall

Often there is a backing to the stall.  Make use of it if it is there.  You need to determine in advance from the organisers what backing there is to the stall you will be allocated.  If there is a wall or other partition, make sure you leave it as you found it.  You can also think about providing your own stall backing with the organiser’s permission.   Using the back of the stall increases the space you have to display your glass.

There are many ways to utilise small spaces at craft fairs. Your imagination will be the only limit.  Think of shop displays, build up, give your glass space, ensure good lighting, use the back of your space.

Glass 101: Glass Formers – The Backbone of Glass

 

Glass 101: Glass Formers – The Backbone of Glass

Posted Krista Grayson on Oct 15, 2019

Glass is a state of matter that exists separately from the conventional forms of metal, polymers, and ceramics. There is a wide and varied number of applications for glass that each require a different set of properties. Glass properties are controlled by the composition. One of the most fundamental changes that can be made to the composition is the basic unit of the glass: the network former. The former can be thought of as the backbone of the glass, and changing this element or compound will fundamentally change the properties of the final material.

How are formers used in glass production?

Glass formers are added to the bulk material to facilitate the formation of a glass and form the interconnected backbone of the glass network. The first paper to discuss these components was written in 1932 by Zachariasen, which is considered a landmark in glass research.1 In this paper, he outlines his theories on glass and classifies the three types of cation that glass networks are composed of: network formers, network modifiers, and intermediates. 

Some common cations that are in network formers are boron, silicon, germanium, and phosphorus. They have a high valence state (meaning they have a surplus or deficit of electrons allowing them to bond easily with other atoms) and will covalently bond with oxygen. Network ions that alter the glass network and intermediates are added to gain special properties in the glass.

Applications of glass formers

Various glass formers are used in varying ratios with modifiers and intermediates to produce a glass that can withstand the rigors of a specific application. For example, a glass suitable for handling high-temperature liquids will be made of a different composition than one that is being used for decorative purposes. 

Silicate glass

Silicate glass is one of the earliest types of glasses and is still produced worldwide today. It is formed of Si4+ ions that are covalently bonded to four oxygen atoms, to form SiO4 in tetrahedral shapes.2 They then connect to other tetrahedra by bridging oxygen ions. If each of the tetrahedra is joined corner to corner, it forms the SiO2 polymorph cristobalite that has significant long-range order. This long-range order produces a highly connected network which leads to a high softening point, a low diffusion coefficient, and a small coefficient of thermal expansion (CTE).

If the silica is worked at lower temperatures, it possesses only short-range order. Intermediates, such as sodium ions, can then be introduced to the silica glass to form alkali silicate glass. This is done through the addition of Na+ ions, each one of which creates one non-bridging oxygen. This reduces the network connectivity, resulting in decreased viscosity, and an increased diffusion coefficient and CTE. There is also increased ionic conductivity and reduced chemical resistance.

Boron oxide glasses

When boron oxide is used as the former, the glass is known as borate glass. In this case, the structure is composed of corner-sharing BO3 triangles connected by bridging oxygen. Borate glass can also be made into an alkali form through the addition of Na+ ions. 

However, in contrast to silicate alkali glasses, the initial addition of these alkali ions has the inverse effect on borate glasses. It causes an increase in network connectivity, a reduction in the CTE and an enhancement in thermal and chemical resistance.3 Alkali borosilicate glass is also known as Pyrex® glass; the improved physical properties make it useful for lab equipment and piping, as well as the tiled coating on the space shuttle.

Phosphate glass

Phosphate glasses are based on P2O5, with CaO and Na2O as modifiers.4 Initially these glasses were used for industrial applications such as clay processing and pigment manufacturing, but more recently they have been put to more specialised uses. Research has found that the constituent ions of phosphate glass are similar to those present in the organic mineral phase of bone.5 This chemical affinity to bone sees these glasses being developed for biomedical use, as the inert nature of the glass is ideal for deployment within the body.

Mo-Sci glasses

Mo-Sci has extensive experience in developing and manufacturing glass produced from various types of formers.6 We offer a number of standard glass compositions such as soda-lime silicate, barium titanate, and type 1A borosilicate, as well as being able to develop custom glass compositions for specific applications. Contact us for more information.

References

1. Zachariasen, W. H. The atomic arrangement in glass. J. Am. Chem. Soc. 54, 3841–3851 (1932). https://pubs.acs.org/doi/pdf/10.1021/ja01349a006
2. Hosford, W. F. & Hosford, W. F. Amorphous Materials. Mater. Sci. 153–167 (2009). https://ocw.mit.edu/courses/materials-science-and-engineering/3-071-amorphous-materials-fall-2015/lecture-notes/MIT3_071F15_Lecture2.pdf
3. Yuntian Zhu. MSE200 Lecture19(CH.11.6,11.8)Ceramics. 19, 1–21 https://people.engr.ncsu.edu/ytzhu/Class-Teaching/MSE200/Lecture19-Nov23.pdf
4. Richard K. Brow. Review: the structure of simple phosphate glasses. J. Non. Cryst. Solids 263–264, 1–28 (2000). https://www.sciencedirect.com/science/article/pii/S0022309399006201
5. Rahaman, M. N. Bioactive ceramics and glasses for tissue engineering. Tissue Engineering Using Ceramics and Polymers: Second Edition (2014). https://www.sciencedirect.com/science/article/pii/B978085709712550003X
6. Mo-Sci Glass Products https://mo-sci.com/en/products

Annealing Previously Fired Items

“Double the annealing soak time for each firing” and “Slow the rate of advance each time you fire” are common responses as a diagnosis when a piece breaks in the slumping process.  It may come from the fact that once fired, It is now a single piece that needs a slower rate of advance on the second firing.  I’m not sure where the idea of doubling the annealing process originates.

You need to think about why you would slow the rate of advance and double the anneal for each subsequent firing of the piece.  This is an investigation of the proposals.

Thickness determines ramp rates and annealing

Annealing soak lengths and cooling rates are related to thickness and complexity.  If no additions or complications are added between the previous and the current firing, there is no reason to extend the soak or decrease the rate of cooling.

You of course, need to consider what lay-up and process you are using in the additional firing.  Have you added any complexity to the piece in the previous or the current firing?  If so, you do need to consider how those changes will affect the firing requirements.

Fire polishing

The question to be asked is, “if the piece was properly annealed in the first firing and shows no significant stress, why do I need to change the firing?”

The answer is, “you only need to slow the heat up because it is a single piece now.”  You do need to know that the existing stress is minimal, of course. A note on stress testing is here.  If there is little or no stress from the previous firing, the annealing and cooling can be the same as the previous firing.  Nothing has changed. You are only softening the surface to a shine.  The anneal was adequate on the first firing, and it will be on the second.

If you are firing a pot or screen melt, you have added a complexity into the firing. This is because of the high temperatures used in the first firing.  It means you may wish to be more cautious about a re-firing to eliminate bubbles, or for a fire polish for the surface.

Frit layers

If you are adding confetti or thin layers of frit or powder you have not significantly changed the piece.  You can re-fire the piece as though you are fire polishing any other piece of the same dimensions.

Additional layers

If you are adding more full layers in subsequent firings, you need to reduce the rate of advance to top temperature.  You also need to extend the soak and reduce the cooling rate according to the new thickness of the piece.  This is because the piece is thicker, so the rate of advance needs to be slower, the time required to adequately anneal is longer, and the cooling rate needs to be slower.  All of these changes in scheduling are to accommodate the additional thickness.

Tack fusing additional pieces

If you are tack fusing pieces to the top of an already fired piece, you need to go slower than you would by just adding a full layer.  Tack fusing pieces to an existing piece adds a significant complication to the firing.  Tack fusing requires a firing for thickness between 1.5 and 2.5 times the actual total height of the piece.  The complexity added is the shading of the base glass from the heat radiating from the elements. 

For example, if your piece from the melt is 9mm/0.375", it would have been annealed with a 90 minutes soak. The first cool would be at 69C/127F per hour, and the second at 125C/225F per hour with the cool to room temperature at 415C/750F. If it shows no significant stress, you can fire polish and anneal in the same way as your initial firing.

But

If you tack fuse pieces on top, then you need to treat the piece as though it were between 15mm/0.625" (a little over 1.5 the thickness) and 25mm/1.0" (a little over 2.5 times) thick.  This would require a soak of 3 or 4 hours.  A cooling rate of between 40C/72F and 15C/27F per hour for the first cooling stage is needed. The second stage between will need a rate between 72C/130F and 27C/49F per hour. The final cooling to room temperature will be between 90C/162F and 240C/432F to room temperature.

Conclusion

If you have made no significant changes in thickness or complexity, the second firing can be the same annealing as the first firing. If you have altered the thickness or complexity of the piece, the second firing will need to be slower.

Further information is available in the ebook Low Temperature Kiln Forming.

Glass 101: Using Glass Modifiers to Change Glass Characteristics

 

Glass 101: Using Glass Modifiers to Change Glass Characteristics

Posted Krista Grayson on Sep 16, 2019

Glass modifiers such as lithium oxide, calcium oxide, and zinc oxide can be used to fine-tune the properties of silicate and borate glass to suit a number of niche engineering applications. In this article we take a look at the ways in which common glass modifiers are used to create high-specification glasses for various applications.

Ordinary glass is a unique material. It’s heat-resistant, exhibiting low thermal expansion and excellent thermal shock resistance; chemically durable; exhibits high electrical resistivity; and of course, is highly optically transparent. These properties have made glass an indispensable material in architecture, labware, electronics, and engineering.

Glass can be further transformed into a true wonder-material through the use of glass modifiers. Just like other materials such as steel, the properties of glass can be precisely tuned and augmented through the careful addition of chemical modifiers to suit a huge array of demanding applications.

Glass structure and composition

The constituents of glass can be broadly divided into three categories: network formers, modifiers, and intermediates.1 Network formers form a highly cross-linked network of chemical bonds and constitute the bulk of the glass. Silicon oxide is the most common network-forming constituent of glass, but glasses based on other oxides such as boron and germanium are also commonly produced.

Modifiers are chemicals that can be added to glass in small quantities to further alter the properties of a glass. These include lithium, sodium, potassium, and calcium; which exist as charged single atoms (ions) amongst the cross-linked network formers, reducing the relative number of strong bonds in the glass and lowering the melting point and viscosity. 

Intermediates; which include titanium, aluminum, and zinc; are chemicals that can behave as network-formers or modifiers depending on the glass composition.2 Glasses are naturally highly disordered, and require a carefully tuned balance of network formers, intermediates, and modifiers to prevent the formation of ordered crystallites within the material.

Effects of glass modifiers

As glass generally acts like a solution, the properties of modified glass can be approximately described by additivity relationships: that is, each ingredient contributes to the bulk properties of the glass by an amount roughly proportional to its concentration.3

Glass modifiers interrupt the normal bonding between glass-forming elements and oxygen by loosely bonding with the oxygen atoms. This creates “non-bridging oxygens,” and lowers the relative amount of strong bonding within the glass. As a result, glass modifiers generally have significant effects on glass properties. 

These include a reduction in melting point, surface tension, and viscosity due to weaker overall bonding within the material. These are some of the primary reasons for using glass modifiers – they make glass easier to work with at lower temperatures without affecting transparency.4 Glass modifiers affect the coefficient of thermal expansion, chemical durability, and the refractive index.

Glass modifiers for high-specification applications

Despite a number of common properties, the unique chemical properties of different glass modifiers can have varying effects on the properties of the glass produced. 

Chemical Durability

The use of alkali metals such as sodium and potassium as modifiers generally reduce the chemical durability of glass, whereas alkaline earth metals such as calcium can increase the chemical durability of glass.5

Resistivity

In electronics, the high resistivity and permittivity of glass lend it to applications in resistors and capacitors. The addition of tellurium, germanium or titanium oxides to glasses in low concentrations have been shown to drastically increase resistivity, making them popular as glass modifiers for ultra-high resistance applications such as hearing aids and infrared detectors.6

Glass for labware

Glass with strong chemical durability and resistance to thermal shock is highly valued in labware manufacturing. The addition of zinc oxide to silicate glass can reduce thermal expansion effects, making it especially resistant to thermal shock. Borosilicate glasses, which use borate as well as silicate as a network former, are also especially thermally resistant and chemically durable, making them a popular choice of material for reaction vessels, test tubes, and other labware.

Specialty optical properties

Some glasses are prized for unusual optical characteristics: zinc-modified glass is widely used in photochromic lenses, while silver, gold, and copper can produce photosensitive glass which changes color in response to incident light.4,7

Bioactive glass

Of particular interest to the biomedical community, bioactive glass is a form of modified glass that closely emulates the properties of the mineral portion of living bone. Bioactive glass is highly biocompatible and forms strong chemical bonds with bone. 

This material consists of around 45% silicate with calcium and sodium acting as the primary modifiers. This results in a comparatively soft glass which can be readily machined into implants for use in the repair of bone injuries.8

Mo-Sci leading precision glass technology

Mo-Sci is a world-leader in precision glass technology and produces a range of high-specification glasses for application in healthcare, electronics, and engineering. With expertise including bioactive glass, high refractive index glass, and fluorescent glass; Mo-Sci is able to produce custom solutions for virtually any glass application. Contact us today with your specifications!

References

1. Karmakar, B., Rademann, K. & Stepanov, A. L. Glass nanocomposites: synthesis, properties, and applications.
2. Kienzler, B. Radionuclide source term for HLW glass, spent nuclear fuel, and compacted hulls and end pieces (CSD-C waste). (KIT Scientific Publishing, 2012).
3. Industrial glass | Britannica.com. Available at: https://www.britannica.com/topic/glass-properties-composition-and-industrial-production-234890#ref608298. (Accessed: 17th May 2019)
4. Phillips, G. C. A Concise Introduction to Ceramics. (Springer Netherlands, 1991). doi:10.1007/978-94-011-6973-8
5. Hu, J. MIT 3.071 Amorphous Materials 2: Classes of Amorphous Materials. https://ocw.mit.edu/courses/materials-science-and-engineering/3-071-amorphous-materials-fall-2015/lecture-notes/MIT3_071F15_Lecture2.pdf
6. Weißmann, R. & Chong, W. Glasses for High-Resistivity Thick-Film Resistors. Adv. Eng. Mater. 2, 359–362 (2000).
7. Photosensitive glass. (1948). https://patents.google.com/patent/US2515275
8. Rahaman, M. N. et al. Bioactive glass in tissue engineering. Acta Biomater. 7, 2355–2373 (2011).

Craft Fair Checklist

www.madeurban.com

There are so many things you need to remember before starting off to the event you have signed up for.  A checklist can help reassure you have everything you need and are prepared for your visitors and customers.

Spread the word

Let everyone know about the fair – your acceptance, your preparations, what you are taking, what else is happening at the event, etc.  The more stall holders talking about the event, the wider the publicity will be, and it should attract more visitors.

Set up at home

Set out the floor space you will have and see how you can make your stand be the best.  Mock-ups at home allow trials of various displays.  Set up one day and leave it for the next.  Your immediate impression the next morning will tell you if it is right.  When you have the display right, photograph it so you have a reference at the setup at the show.

Design your own banner

Most big organisers will have a generic name board for your stand.  Everyone has that.  Your pitch can stand out if you have designed a banner which reflects your glass work and business logo.  It needs to be boldly visible and state the business name clearly.

Tool kit 

You need to have a box or bag of all the things you need to set up and sustain you for the event.  There are the things you need to operate during the show - a float of cash, pens, business cards, Publicity material, blu-tac, scissors, string, strong tape, wet wipes, polishing cloths, pens, phone charger, and a small notebook, tablecloth, price labels, bags, packaging,  a card reader, smart phone or internet connected tablet, directions to the venue, etc.  Your list will vary to some extent for your needs, but will be much the same for large and small events.

You need to think about yourself too.  Bring bottles of water, snacks, chewing gum or mints, tissues, a folding chair, anything else you need for sustenance for 6- to 10- hour days;  and a positive attitude.

Make it possible to carry all of it

Remember you have your set-up materials – stands, boxes, supports, and survival bag.  You also have to get your glass and packaging into the premises too.  How are you going to manage? Will a folding trolley be needed? Maybe some other carrying method will be better.  Pack things up and practice transporting them for a distance.  If it is too heavy, try other methods such as breaking the materials into smaller units.

Have your directions to the event with you

You need to be sure how to get to the venue to avoid any panics.  Make sure you have plenty of time to get to the place.  Being early allows you to have a rest and calm down after setting up and before the visitors enter.  Give yourself plenty of time to unload and park the car – everyone else is trying to do the same thing as you and at the same time.

Pricing 

Make your price list days before the fair, ideally as soon as you have finalised what glass you are taking.  Make sure all the glass is clearly priced, so the less confident buyers don’t have to ask. If you are selling online, the prices should be the same. You may want to offer discounted prices at the event, but the ticket price should be the same as online.

Business details

Bring business cards to hand out to people who cannot make the decision to buy on the day.  They may decide to buy later. A discount code written onto the card may stimulate a later purchase from the online shop.  Have publicity material available too – something about you, your glass, and your business.  Price lists are useful if you meet buyers and wholesalers.

Card reader

A method to take card payments is essential. A sign or logo indicating that you take card payments encourages people to purchase.  If you don’t already have one, give yourself enough time to get it, as it often takes at least a month.  And you have to get familiar with it before the show.

Web presence

Make sure that your website, your shop and your social media are up to date.  Events often cause more traffic to your sites, so they need to be ready before you leave for the event.  This means hiding anything that is one-off or difficult to replicate.  Sometime after the show they can re-appear.

Conversations

Be ready for the people you will be meeting with a variety of starters for the conversation with different visitors.  You will probably have a different conversation with a buyer than with the general run of visitors.  You want a conversation to get feedback on your glass and other things relevant to your glass, display and general presentation.  These also help discover what may fit the people who want to buy, or comment on your work in ways that can help you improve or even start new glass lines.  Have a notebook to record the feedback you get as soon as you can at the event.

Plan friendly, but not pushy conversation openers.  You can offer help in describing the qualities of your glass, rather than how it was made.  Be prepared to talk about yourself, your inspirations, how you work, etc.  Be interested in the visitors – their likes, desires, what they are looking from the event. 

It is from these conversations that you can expand your mailing list.  The people you have pleasant conversations with will be willing to join your mailing list and the social media you participate in.  Enjoy your event!

Engage with your neighbours 

If you are on your own for a long day, you will need help from them to cover for your toilet breaks at the least.  Friends you make at shows can become long-term and can be a source of information when you have questions.  They don’t have to be glass workers.  It is a good way to business network and get mutual support.

Based on an article written by Camilla from Folksy blog.folksy.com

Glass 101: Glass Processing Temperatures

 

Glass 101: Glass Processing Temperatures

Posted Rebecca Molt on Aug 14, 2019

Glass is an amorphous solid with no long-range order. This lack of order is what differentiates a glass from a crystalline solid. For example, when silicon dioxide is cooled slowly through the crystallization temperature, it is allowed to form crystals, giving the solid a geometric structure throughout the material. When silicon dioxide is heated and then rapidly cooled, it’s ordered crystalline structure is unable to reform and it becomes an amorphous solid (glass). [1] 

Glass goes through different transitions during melting. The glass transition temperature, softening point, and crystallization temperature are all part of the glass forming process. Careful maneuvering through these steps is critical to the formation of a stress-free glass product.

Glass Transition Temperature

The glass transition temperature (Tg) characterizes a range of temperatures where an amorphous material transitions from a hard brittle state to a viscous state relative to increasing temperature.[2] The solid begins to exhibit viscoelastic properties above Tg. When disordered molecules are below Tg, they have less energy, and the molecules aren’t able to move into new positions when stress is applied. When above Tg, the molecules have more kinetic energy, allowing them to move in order to alleviate applied stresses.[3] The annealing temperature is selected based on the glass transition temperature, allowing any stress to be released before completely cooling the glass.

Littleton Softening Point

The Littleton softening point (Ts) of glass is the temperature at which the glass moves under its own weight. As a glass is heated, the glass flows more easily. The resistance to flow is known as viscosity. At the softening point, the glass has a viscosity of 107.6 poise.[4] This point is often used to define the working range of the glass. Once the glass has reached the softening point, it is malleable without melting.

Crystallization Temperature

The crystallization temperature (Tx) characterizes the onset of crystallization. Crystallization is the process of forming a solid. The molecules become highly organized into a geometric structure known as a crystal. This occurs in two steps. The first step is the nucleation or “seed” formation. Nucleation can be influenced by the initiation of a secondary phase formation within the matrix or the introduction of an outside substance, such as particles from the crucible. The second step is crystal growth, which is the growth around the original nucleation sites in layers.[5] Crystallizing brings the melt down to a lower energy state. If a melt crystallizes it will not become a glass since glass is a disordered solid. Crystallization is avoided by rapidly quenching through the glass transition region. 

Coefficient of Thermal Expansion

The coefficient of thermal expansion (CTE) describes a material’s change in shape, area, and volume in response to temperature change.[6] Heat is a type of kinetic energy. When a material is heated, its kinetic energy increases which causes the molecules to vibrate at a higher frequency. The molecules then take up more space than usual. The reverse is true when cooling a material. When cooled, the molecules have less kinetic energy, and they contract, taking up less space....

Mo-Sci Corporation’s extensive glass knowledge and research experience make it a perfect candidate for custom development needs. Mo-Sci has partnered with companies across a wide variety of industries, creating custom glass solutions for unique applications. Contact us for more information on how we can help with your next glass product.[8]

References

1. NDT Resource Center, http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/solidstate.htm, Center for NDE, Iowa State University.
2. ISO 11357-2: Plastics – Differential scanning calorimetry – Part 2: Determination of glass transition temperature (1999).
3. The Glass Transition. https://pslc.ws/macrog/tg.htm. Accessed: 21 June 2019.
4. Technical Glasses: Physical and Technical Properties | SCHOTT Technical Brochure. https://www.us.schott.com/d/tubing/ffed51fb-ea4f-47d3-972e-5a2c20f123f5/1.0/schott-brochure-technical-glasses_us.pdf. Accessed: 21 June 2019.
5. Crystallization |Reciprocal Net http://www.reciprocalnet.org/edumodules/crystallization/. Accessed: 24 June 2019.
6. Tipler, Paul A.; Mosca, Gene (2008). Physics for Scientists and Engineers – Volume 1 Mechanics/Oscillations and Waves/Thermodynamics. New York, NY: Worth Publishers. pp. 666–670. ISBN 978-1-4292-0132-2.
7. Novel Sealants to Significantly Improve the Lifetime and Performance of Solid Oxide Fuel Cells | Mo-Sci Blog https://mo-sci.com/novel-sealants-Improve-solid-oxide-fuel-cells. Accessed: 25 June 2019
8. Mo-Sci Corporation Website https://mo-sci.com/en/custom-development. Accessed: 24 June 2019.

Calibrating your new kiln

My new kiln fires differently than my existing one(s).

Each kiln will be different in minor or major ways.  Suggested schedules are only starting points, even though they worked in your previous kiln. You need to learn about your new kiln’s characteristics in the same way you did with your first kiln. There are a number of ways to do this.

Many people recommend making test tiles for the different levels of fusing that you use and at different temperatures to determine which is the best for your new kiln.  Additionally, you need to note the rate(s) at which you fired these samples to make the test tiles accurate representations of firings.  Yes, these will be good references.  And yes, they are valuable if you have the time for all these firings.

 Idle Creativity

Observation during the firing of test tiles is the best and quickest way to discover how your new kiln is performing at various temperatures.  In one firing you can note the temperatures at which the various tack levels occur, and the contour and full fuse temperatures.  You can even take pictures through the peep hole of your kiln (as long as you don’t put the camera too close to the kiln!).  This procedure will make knowing your kiln much quicker and accurate than unobserved multiple firings.

To make use of the notes of the temperatures where the results were achieved in the test firing, back off 10°C (or 20°F) from the observed temperature and add 10 minutes processing time.  You may find after a few uses of these temperatures you may want to adjust the temperature a bit more, but you will have done the major experimental work in one firing.

It is a good idea to set up other test tiles and run the experiment again at a slower rate of advance.  This will give you information about how the different rates of advance affect the processing temperature and the look and texture of the piece, especially on the bottom.  The texture imparted at different processing temperatures becomes more important in slumping and draping processes.

In another firing you can set up various moulds and observe when the slumps or drapes are complete. Recording this information lets you know slump temperatures for various styles and spans of moulds.  Make sure you record the temperatures that the pieces slump fully into the mould. You can then back off 20°C from those points and add 30 minutes as a starting point for you actual slumping firings.

New kilns require experience to know what the appropriate temperatures are.  Buy setting up test tiles you can observe in one firing the various levels of fuse from tack to full fuse, so saving lots of firing time.

Further information is available in the ebook: Low Temperature Kiln Forming.

Glass 101: An Introduction to Glass

 

Glass 101: An Introduction to Glass

Posted Krista Grayson on Jul 17, 2019

Everyone knows what glass is…or do they? We are all surrounded by glass in a myriad of forms and serving a diverse array of functions, from jars and glasses to windows and TV screens, but do we really know much about it? Glass has become so ubiquitous that it is widely accepted as an everyday commodity. Consequently, most of us take it for granted without considering what it is or how it shows such amazing properties and versatility.

Through the ages, glass has provided answers to many technological challenges and enabled unbelievable advances across most areas of our lives.1,2 However, despite being at the center of an ongoing success story, glass receives little attention from the majority.

What is glass?

Glass is commonly categorized as a type of ceramic, but it is not like any other ceramics. Ceramics generally have a crystalline structure and are opaque, whereas glass has a non-crystalline atomic structure and is transparent. Furthermore, glass exhibits a range of remarkable properties that set it apart from other ceramics. In a perfect state, glass is mechanically very strong, even when subjected to extreme changes in temperature, and has a hard surface that is resistant to abrasion and corrosion. Paradoxically, it is also elastic, being able to give under stress (up to a breaking point) and then rebound to its original shape. Glass also has extensive optical properties, is heat-absorbent and an electrical insulator.3

Glass is so unique that it cannot be simply defined. It is neither a crystalline solid nor a liquid; it is a disordered, amorphous solid. It is this amorphous structure that gives glass its unique properties. Neither can the composition of glass be described since there are infinite varieties of glass. A current database lists over 350,000 types of known glass and new workable glass compositions are being developed every day.

The production of glass

Glass is formed when the constituent parts are combined by intense heating and then rapid cooling. The rapid cooling immobilizes the atoms of the glass before they have a chance to assume a regular crystalline structure. This can occur naturally, as in the case of fulgurite that is formed by lightning striking sand, and obsidian that arises from the rapid cooling of volcanic lava.

Man-made glasses are produced from varying mixtures of oxides. Although the precise chemical composition varies widely between different types of glass, it typically includes three components: a former, a flux and a stabilizer. Glass formers, such as silicon dioxide (silica), make up the largest proportion of the mixture and provide the transparency. Fluxes, such as sodium carbonate (soda) lower the temperature at which the formers will melt. Stabilizers, such as calcium carbonate (lime) provide the strength and make the glass water resistant. Without the inclusion of a stabilizer, water and humidity will attack and dissolve the glass.4

Immediately after glasses are batched and melted, they are slowly and evenly cooled. This process is known as annealing. This is an important step that enhances the strength of the glass by reducing internal stresses. It ensures that sections of varying thickness cool at the same rate. This avoids the development of steep temperature gradients that could cause the glass to crack.

Types of glass

The precise chemical composition of the mixture melted to produce glass determines the mechanical, electrical, chemical, optical, and thermal properties of the final product. Glass can thus be manufactured with broad-ranging characteristics. Through careful selection of the basic initial mixture and additives used in production, glass is produced with properties and structures to meet the requirements of specific applications.3

Although there are many thousands of different glass compositions, glass can be categorized as belonging to one of the six basic types, based on the chemical composition that endows it with specific properties.5

Soda-lime glass

Soda-lime glass is the most common, and least expensive, type of glass, accounting for 90% of all glass made. It usually contains 60–75% silica, 12–18% soda, and 5–12% lime. This is the type of glass used to make bottles and windows. It is mechanically strong but does not have good resistance to high temperatures, sudden changes in temperature, and corrosive chemicals.

Lead Glass

Lead glass (more commonly known as crystal) contains at least 20% lead oxide, which makes the glass brilliant, resonant, and heavy. Although lead glass, like soda-lime glass, will not withstand high temperatures or sudden changes in temperature, it exhibits excellent electrical insulating properties. Consequently, it is commonly used for electrical applications. It is also used for thermometer tubing and art glass.

Borosilicate glass

The addition of at least 5% of boric oxide to a silicate glass gives it high resistance to temperature change and chemical corrosion. Borosilicate glass is not as convenient to produce as either lime or lead glass, but is useful for pipelines, light bulbs, photochromic glasses, sealed-beam headlights, and vessels for laboratory or kitchen use.

Silica glass

Removal of almost all the non-silicate elements from borosilicate glass after normal melting and forming produces 96% silica glass. The resulting pores are sealed by reheating the glass to 1200° resulting in glass that is resistant to heat shock up to 900°C. 96% silica glass is used for the outer panes of the forward windshields of space shuttles to enable them to withstand the high temperatures reached during atmospheric re-entry.6

Aluminosilicate glass

Similar to borosilicate glass is aluminosilicate glass that includes aluminum oxide in its composition. Aluminosilicates are more difficult to manufacture than borosilicate glass, but have even greater chemical durability and can withstand higher operating temperatures. Aluminosilicate glass can also be used as a resistor in electronic circuits.3

Fused silica glass

Fused silica glass is the most difficult type of glass to produce, and so it is the most expensive of all glasses. Fused silica glass is pure silicon dioxide in the non-crystalline state and can withstand temperatures up to 1200°C for short periods. Fused silica is used to create astronomical telescopes, optical waveguides, and crucibles for growing crystals.6

Glass additives

Additives can be used to change the characteristics of glass. This may be done be for aesthetic purposes, for example, heavy metals, such as lead or manganese may be added to give the glass color. It may also be altered for functional purposes, for example, the addition of selenium makes the glass a light-sensitive conductor of electricity; a feature that forms the basis of photocopying.

Versatility of glass

Glass has an extensive range of potential forms and shapes. Its desirable properties can be manipulated during manufacturing, such as mechanical strength and chemical stability. This has led to the development of novel glass formats for use across an entirely new scope of applications.

Controlled-pore glass, which is porous glass with a sharply defined and adjustable pore size, can be used as a support for solid-phase oligonucleotide synthesis7 and as a stationary phase for a variety of chromatography techniques.8,9 Hollow glass biospheres have unique optical properties that have enabled the development of new research techniques, which hold huge potential for analytical devices of the future.10

Glass is also increasingly being adopted for a range of applications in medicine and dentistry. Bioactive glass is biocompatible and demonstrates antimicrobial activity. Furthermore, it can bond with both soft tissue and bone to promote healing. Bioactive glass has thus become an invaluable tool in tissue engineering and bone implants11 as well as in dental reconstruction procedures.12 It is also used in toothpaste and dental fillings to strengthen enamel and reduce bacterial colonisation.13

The future of glass

Glass has become the material of choice for solving a range of technological challenges. It is lightweight yet has the potential for strength, durability and optical clarity and its precise properties can be fine-tuned to meet a specific need. It can also be produced in a range of very different formats, including flat sheets, fine tubes, beads, and powder.

The versatility of glass has enabled incredible achievements, but the journey has by no means reached its end. With new production techniques and types of glass being continually developed, potential applications of glass products continue to expand and facilitate further remarkable advances. We are already benefitting from great interactive user experiences through the glass screens of mobile phones and tablets, but prototypes are now in development for touch-activated glass surfaces through which a range of digital devices can be accessed. Similarly, glass screens have been developed that provide a medium for virtual and augmented reality experiences.

Scientists continue to take advantage of the unique characteristics of glass, redefining what is possible. The latest projects include cleaning up nuclear waste by vitrification and using glass to develop safer batteries.

With a long and successful history, glass is still an active field of discovery and innovation with a future of exciting and ever-expanding capabilities.

Mo-Sci is a world leader in high-quality precision glass technology and produces a wide range of specialist glass products, the precise composition of which can be tailored to meet specific requirements.14

References

1. Rasmussen SC. Origins of Glass: Myth and Known History. In How Glass Changed the World. Springer 2012. Briefs in History of Chemistry, DOI: 10.1007/978-3-642-28183-9_2
2. Main D. Humankind’s Most Important Material. Object Lessons 2018. Available at https://www.theatlantic.com/technology/archive/2018/04/humankinds-most-important-material/557315/
3. What is Glass | Corning Museum of Glass. All about Glass. https://www.cmog.org/article/what-is-glass
4. Chemisty of Glass | Corning Museum of Glass. All about Glass. https://www.cmog.org/article/chemistry-glass
5. Types of Glass | Corning Museum of Glass. All about Glass.
   https://www.cmog.org/article/types-glass
6. Glass and The Space Orbiter | Corning Museum of Glass. All about Glass.
   https://www.cmog.org/article/glass-and-space-orbiter
7. Grajkowski A, et al. A High-Throughput Process for the Solid-Phase Purification of Synthetic DNA Sequences. Curr Protoc Nucleic Acid Chem. 2017 Jun 19;69:10.17.1-10.
8. Zucca P and Sanjust E. Inorganic Materials as Supports for Covalent Enzyme Immobilization: Methods and Mechanisms. Molecules 2014, 19, 14139—14194.
9. Igata Y, et al. A ‘catch and release’ strategy towards HPLC-free purification of synthetic oligonucleotides by a combination of the strain-promoted alkyne-azide cycloaddition and the photocleavage. Bioorg Med Chem. 2017 Nov 1;25(21):5962—5967.
10. Ward JM, Dhasmana N, Chormaic N. Hollow core, whispering gallery resonator sensors. The European Physical Journal Special Topics 2014;223(10):1917–1935.
11. Rahaman MN, et al. Bioactive glass in tissue engineering. Acta Biomaterialia 2011;7:2355—2373.
12. Sohrabi K, et al. An evaluation of bioactive glass in the treatment of periodontal defects: a meta-analysis of randomized controlled clinical trials. J Periodontol 2012; 83: 453—464.
13. Chatzistavrou X, et al. Fabrication and characterization of bioactive and antibacterial composites for dental applications. Acta Biomater. 2014;10:3723–3732. Available at https://www.ncbi.nlm.nih.gov/pubmed/24050766
14. Mo Sci Corporation website. http://www.mo-sci.com/en/products