Making Circles from Fused Squares

Dennis Brady has done a lot of work on predicting the size of circles resulting from stacking squares of glass and taking them to full fuse for enough time to allow flattening of the stacks.  This may be up to half an hour at 815°C for Bullseye.  Some observation will be required.

Stacks of 12mm/ 0.5" squares arranged at 45° to each other and taken to a full fuse:

• 1 layer should produce a 10mm/ 0.375" circle
• 2 layers should produce a 12mm/0.5" circle
• 3 layers should produce a 16mm/0.6" circle
• 4 layers should produce a 18mm/0.7" circle

 Stacks of 19mm/0.75" squares arranged at 45° to each other and taken to a full fuse:

• 1 and 2 layers will not fully round
• 3 layers should produce a 28mm/1.1" circle

 Stacks of 25mm/1" squares arranged at 45° to each other and taken to a full fuse:

• 4 layers should produce a 40mm/1.6" circle
• 5 layers should produce a 45mm/1.75" circle
• 6 layers should produce a 50mm/2" circle

 Stacks of 32mm/1.26" squares arranged at 45° to each other and taken to a full fuse:

• 4 layers should produce a 48mm/1.9" circle
• 5 layers should produce a 52mm/2" circle
• 6 layers should produce a 58mm/2.3" circle

 Stacks of 37mm/1.5" squares arranged at 45° to each other and taken to a full fuse:

• 4 layers should produce a 40mm/1.6" circle
• 5 layers should produce a 45mm/1.8" circle
• 6 layers should produce a 50mm/2" circle

 Stacks of 50mm/2" squares arranged at 45° to each other and taken to a full fuse

• 4 layers should produce a 75mm/3" circle
• 5 layers should produce a 85mm/3.3" circle
• 6 layers should produce a 95mm/3.75" circle
• 7 layers should produce a 102mm/4" circle
• 8 layers should produce a 105mm/4.125" circle

 Based on work done by Dennis Brady

I had a few queries about this regular progression and wondered if it applied to opalescent as well as transparent glass. I set up a few tests in my kiln. I fired them at 400C to 815C for 10 minutes.

I got the following results. 

You can see that the opalescents require more heat work than the transparent. If you are making circles with both transparent and opalescent you will need more time at the top temperature - perhaps 30 to 45 minutes.  This results from the greater viscosity of the opalescent colours.

I also tried making ovals from rectangular pieces oriented at about 25 degrees to each other. You can see they were not successful with a 10 minute soak.  

Bubbles in Bottle Slumps

 Any suggestions on how to avoid getting the oblong bubble under the neck of the bottle? This was my first try and I’m really happy with clarity, no devitrification in these.

I used this schedule:

Fahrenheit                    Celsius

300/1150/30                167/620/30

200/1370/20                111/740/20

400/1450/20                222/787/20

AFAP/950/60                AFAP/510/60

150/800/0                    63/427/0

300/100                       167/55/off

The bubble is kind of cool but not sure what it will do when I put it in a bottle mould.

 

To minimise the bubble, you need a bubble squeeze.  There isn't one of sufficient length or at the right temperature in the schedule. The softening point of bottle glass is approximately 720C. Starting the bubble squeeze at ca. 670C/1240F and progressing slowly (ca.50/90F or less) to 720C/1340F may give a better bubble squeeze. 

Also, the anneal soak is a bit low. Bottle glass and float glass both have annealing points of about 550C. You might make use of a lower annealing soak temperature to reduce the cooling time.  It is usually possible to anneal 30C below the published annealing temperature.  In this case that would be 520C.  

There is pretty thick glass in some places due to the way the bottom and neck of the bottle form. You may want to extend your anneal soak to one for 12mm/0.5”.  The soak time for this is 2 hours.  The first cooling segment would be 55C/100F per hour to 475C/888F if you use 520C/970F as the annealing soak.  The second cool segment should be at 99C/180F per hour to 420C/790F.  And the final rate at 330C/600F to room temperature.  It is important to include all three stages of cooling.  The research for my book Low Temperature Kilnforming (Or directly from stephen.richard43@gmail.com) has shown that to get the best stress-free results  use all three stages of cooling.

Bubbles at the shoulder of the bottle are common.  The change in circumference of the bottle at the shoulder means there is a greater amount of glass to “compress”.  Bottles with tapered circumference at the top of the bottle have fewer problems with creating bubbles.  The abrupt change in size at the shoulder causes bubbles to be more common.  A long slow bubble squeeze will allow the shoulder to form more closely in line with the neck. 

There are other things you can do to help avoid the bubbles. One thing is to insert a thin kiln washed wire into the neck of the bottle. This gives a path for the air to escape and allows you to pull it out, although a mark will be left.  You could also think of drilling a hole in what will be the underside at the shoulder to allow air out to the shelf. It does not need to be a big hole.

Bubbles at the shoulder of a slumped bottle are a common problem. It results from the greater amount of glass that has to slump into the space.  This leaves a cavity.  Slower bubble squeezes can help, as well as various venting methods.

Drop Vase Design for Opalescent Glass

Credit: Missy Mac Glass on Folksy

When making a drop vase in opalescent glass, the design needs to be on the outside.  This will require ensuring the design will be on the bottom when suspended on the drop ring.

It is possible to build the whole piece as normal with the design on the top and fire it.  Then you can turn it over to make sure the design is facing downwards. 

To get a crisper design for the outside the flip and fire technique can be used.  Build from the outer layers to the inner layers.  You are building upside down. Place the design to be seen on the outside of the drop vase down on the prepared shelf first.  Follow this up by placing the inner layers in order from the most outside to the most inside layers.

These instructions rely upon firing the blank first rather than building on the drop ring.

However, you can build on the ring if you need to save one of the two long firings.  Only one modification is required.  Place a sheet of clear down first.  Assemble the design as for a flip and fire technique, i.e., outside layers first, inside layer last.  

This will require a slow heat up to ensure you have allowed enough time for the air to be squeezed from between all the layers and that all the glass at the same temperature before the drop begins.  Sprinkling a fine layer of clear powder over the clear is a good way to assist allowing the air out.  Place the design pieces down before applying the powder. 

This is not the best way to make drop vases, but it can work with care in placing the decorative pieces and applying the powder.

Home Made Frit Maker

Recently, when looking for a small frit maker, no shop had one in stock.  Having heard of making one from plumbing pipes, I went in search of material.  I came across stainless steel pipe and caps.

 

The practical size seemed to be 50mm.  Short sections of threaded pipe were available with matching caps.  That forms the containment cylinder.

 

A threaded 25mm pipe and cap can be fitted loosely into the larger one, and so forms the plunger or piston.

 

There needs to be a handle.  It could be a turned piece of wood to fit the inside of the pipe.  In this case, I obtained a reducing connector to fit a 12mm pipe to the plunger and topped it with another cap. 

The whole was put together in less than a minute, once all the parts were assembled.

The completed frit maker

Galvanised pipe would be cheaper but carries the possibility of introducing zinc into the frit.  Stainless steel risks introducing non-magnetic particles into the frit.  As I sieve out powder from my own frit making before washing, I am not too concerned about steel contamination.  If you want powder, use uncoated mild steel so the contamination can be drawn out with a strong magnet.

Silberschnitt Runners

 
The use of the highly acclaimed Silberschnitt cut runners requires a bit of experience to get the best from them.  They are at their best on inside curves and thin strips.  This is a few notes on how to make best use of the runners.

 

 
Always use the runners with the name visible to you.  This is the right way up.
 

Make use of the adjustable bar at the top of the runners.  Rotate the adjustable bar to be at right angles to score line.  This means the pliers do not have to be at a particular angle to the score line, which has advantages in tight areas.
 

Each press of the handles opens only a small run of the score.  Excessive pressure risks breaking glass and reducing the life of the pads

 

Move the runners along to the front edge of the opened score and press again.  Work your way all along the curve adjusting the angle of the bar as you go.  This progressive opening of the score line gives a break with almost no flares.
 

These runners are much better than the plastic ring star breakers, because there is much more control over angle of pressure.
 
Note: make sure you get replacement pads when you buy, they are robust but do wear out over time.).
 
 
Silberschnitt running pliers are excellent but require some experience to get the best from them.

Hazards of Flux Fumes

Note:  These health risks are those associated with industrial exposure – frequent and for extended periods.  They do not apply directly to occasional and shorter periods of exposure.

Risks are assessed as acute and chronic.  Acute means immediate reaction.  Chronic means the effects are cumulative and may take years to appear.
 

Composition of Flux

The major components of commercial flux are varying combinations and proportions of zinc chloride (or ammonium chloride), hydrochloric acid, phosphoric acid, citric acid, and hydrobromic acid.  It comes in many forms and many brand names.  It is important to use water soluble flux in stained glass work to enable thorough cleaning.
 
 

 

Zinc Chloride Risks

Zinc chloride inhalation from smoke screen generators or smoke bombs may cause transient cough, sore throat, hoarseness, a metallic taste, and chest pain.  Exposure to high zinc chloride concentrations produces a chemical pneumonitis with marked dyspnoea, a productive cough, fever, chest pain and cyanosis. Pneumothorax and the adult respiratory distress syndrome (ARDS) have been reported. Fatalities have occurred….
http://www.inchem.org/documents/ukpids/ukpids/ukpid86.htm#:~:text=Toxicity%20Zinc%20chloride%20is%20corrosive,anorexia%2C%20fatigue%20and%20weight%20loss.
 

Ammonium Chloride Risks

Exposure to Ammonium Chloride is moderately hazardous, causing irritation, shortness of breath, cough, nausea, and headache. Most exposure is a result of contact with the fume form of this chemical (Ammonium Muriate Fume and Sal Ammoniac Fume), which is a finely divided particulate dispersed in the air. The fumes are capable of causing severe eye irritation. Consistent exposure can cause an asthma-like allergy or affect kidney function.
 
In the event of accidental contact, get immediate medical attention and follow these first aid measures:
·        Skin Contact: Immediately flush skin with water and disinfectant soap and use an emollient on irritated area.
·        Eye Contact: Rinse eye(s) with water for at least 15-20 minutes. Protect unexposed eye.
·        Ingestion: Rinse mouth thoroughly with water. Do NOT induce vomiting.
·        Inhalation: Move to fresh air and administer artificial respiration if needed.
https://www.msdsonline.com/2017/05/05/chemical-spotlight-ammonium-chloride/#:~:text=Exposure%20to%20Ammonium%20Chloride%20is,particulate%20dispersed%20in%20the%20air.
 
 

Hydrochloric Acid Risks

Hydrochloric acid is corrosive to the eyes, skin, and mucous membranes.  Acute (short-term) inhalation exposure may cause eye, nose, and respiratory tract irritation and inflammation and pulmonary edema in humans.  Acute oral exposure may cause corrosion of the mucous membranes, oesophagus, and stomach and dermal contact may produce severe burns, ulceration, and scarring in humans.
 

Acute Effects: 

Hydrochloric acid is corrosive to the eyes, skin, and mucous membranes.  Acute inhalation exposure may cause coughing, hoarseness, inflammation and ulceration of the respiratory tract, chest pain, and pulmonary edema in humans.  Acute oral exposure may cause corrosion of the mucous membranes, oesophagus, and stomach, with nausea, vomiting, and diarrhoea reported in humans.  [Skin] contact may produce severe burns, ulceration, and scarring…. Acute animal tests in rats, mice, and rabbits, have demonstrated hydrochloric acid to have moderate to high acute toxicity from inhalation and moderate acute toxicity from oral exposure.

 

Chronic Effects: 

(Non cancer): Chronic occupational exposure to hydrochloric acid has been reported to cause gastritis, chronic bronchitis, dermatitis, and photosensitization in workers.  Prolonged exposure to low concentrations may also cause dental discoloration and erosion.  Chronic inhalation exposure caused hyperplasia of the nasal mucosa, larynx, and trachea and lesions in the nasal cavity in rats.  The Reference Concentration (RfC) for hydrochloric acid is 0.02 milligrams per cubic meter (mg/m 3) … The RfC is an estimate … of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime.  It is not a direct estimator of risk but rather a reference point to gauge the potential effects.  At exposures increasingly greater than the RfC, the potential for adverse health effects increases.  Lifetime exposure above the RfC does not imply that an adverse health effect would necessarily occur.
https://www.epa.gov/sites/production/files/2016-09/documents/hydrochloric-acid.pdf
 

 
Phosphoric Acid Risks

Phosphoric acid can be very hazardous in the case of skin contact, eye contact, and ingestion. It can also cause irritation if vapours are inhaled. This chemical can cause damage to the skin, eyes, mouth, and respiratory tract. Because of the potential hazards posed by this chemical, it is important to use care when handling it.
 
Repeated or prolonged exposure to phosphoric acid mist can lead to chronic eye irritation, severe skin irritation, or prolonged respiratory tract issues.  In case of accidental exposure to phosphoric acid, follow these first aid guidelines:

Inhalation — Seek fresh air and immediate medical attention.

Eye Contact — Remove contact lenses if present. Immediately flush eyes with plenty of water for at least 15 minutes and get medical attention.

Skin Contact — Wash skin with soap and water. Cover any irritated skin with an emollient. Seek medical attention. 

Ingestion — Do NOT induce vomiting. Never give anything by mouth to an unconscious person. Seek medical attention if any adverse health symptoms occur.
https://www.msdsonline.com/2015/06/17/phosphoric-acid-safety-tips/
 
  

Citric Acid

Citric acid can be a minor skin irritant, causing itchy skin and even minor burns to those that are sensitive to it. Hands should be washed immediately if citric acid comes into contact with bare skin. Protective gloves should be worn during handling to avoid any accidental contact. The acid can also irritate the walls of the throat if ingested or burn the lining of your stomach if ingested in large quantities.
 
Eye Irritation - Citric acid is a severe eye irritant. Accidental contact with the eyes can occur … by touching the eyes after the acid has contacted the fingertips. …  Protective eyewear should be worn when working with citric acid under laboratory conditions. Eyes should be flushed with water immediately if they happen to come in contact with the acid.
https://sciencing.com/hazards-citric-acid-8165149.html

Remember that this irritation is equivalent to squirting lemon juice into your eye.  It is not a chronic risk.
 

Hydrobromic Acid (HBr)

Hydrobromic acid and hydrogen bromide gas are highly corrosive substances that can cause severe burns upon contact with all body tissues. The aqueous acid and gas are strong eye irritants and [tear producers]. Contact of concentrated hydrobromic acid or concentrated HBr vapor with the eyes may cause severe injury, resulting in permanent impairment of vision and possible blindness. Skin contact with the acid or HBr gas can produce severe burns. Ingestion can lead to severe burns of the mouth, throat, and gastrointestinal system and can be fatal. Inhalation of HBr gas can cause extreme irritation and injury to the upper respiratory tract and lungs, and exposure to high concentrations may cause death. … Hydrogen bromide has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans.
https://web.stanford.edu/dept/EHS/cgi-bin/lcst/lcss/lcss47.html#:~:text=The%20aqueous%20acid%20and%20gas,gas%20can%20produce%20severe%20burns.
 
 
 

Precautions to be taken by glass workers

The risks outlined above are related to dealing with concentrated amounts of the materials in industrial settings.  Risk levels are much reduced in the craft setting.  The risks are mainly centred on breathing and eye exposure. 
 
It is important to wear masks of the quality that will deal with inorganic fumes.  In Europe these are designated as FFP2.  In general masks rated at N95, P95, or R95 are the level required for filtering out 95% of particles that are larger than 3microns.  Dust masks are not sufficient protection. 
 

Usually overlooked is eye protection.  The risks outlined here show that risks to eyes are equal to - or in some cases greater than – respiratory ones.  Eye protection is as important as breathing filters.  To fully protect the eyes, goggles of some sort are the minimum requirement.  Glasses will not be sufficient to prevent fumes reaching eyes.

 
For a “one stop solution” a full-face mask may be the simplest solution.  The filters on these are long lasting and replaceable.  They can be put on as one unit and are available in various face sizes.
 

At soldering temperatures, there are no lead or tin fumes created.  It is the fumes from the flux that are the risks in soldering.  These risks are small and can be dealt with by using adequate ventilation, masks, and goggles.

Choosing a Name for Your Business

Naming your business requires some thought.  Many people give their activity a name before it really is a business, often while it is a hobby.  At the point of deciding on creating a business, is the time to fully consider the name. It is important to choose the right name for your business. It can create a good first impression for customers and provide a great foundation for building your brand.  You can be creative when choosing the name. However, it needs to be appropriate and work on all types of marketing material, from signage to stationery. There are structured ways of choosing a name.

Personal Name

Many creative sole traders use their own name as their business name. It is easy and often creates the personal connection sought for by buyers.  Using your own name gives your business a more arts oriented and personal touch. Sometimes people are already ‘known’ under their own name prior to beginning the formal business, e.g., Amanda J Simmons.
 

Initials

Some designers use their initials or attach their discipline to their name or initials to add some clarity to what they do, e.g., MJM Ceramics. Others prefer a business name, so that it is less personal and not based around one individual. This can appear as more professional and allows the business to grow beyond the individual.
 
Some people use both - their surname for artistic one-off work, and a business name or brand name if they want to have a more general approach for multiples. You can be self-employed (e.g., using your own name) and run a limited company (with a business name) at the same time.
 
Even though associating your name in these two ways are attractive, more consideration is needed to ensure you are really on the right track.  Naming your business, or even a new collection, can be difficult. There are some practical tips to help you on your way:

 

Reflect on your vision, values, and passions

You have already pulled out these things in looking at your life goals and vision. Now you need to apply them to a name search.  A method that may help is to write down ten important descriptive words about these values, passions, and your vision. This is a starting point for thinking about the best words for the business.  These words will probably not come immediately.  You might want to involve others in a kind of brainstorming to develop a group of key words.  You need to consider how this name will look in the future as your business develops.

 

cREDIT: BUSINESS NAMES

The name needs to reflect you and your market.

“A good business name reflects who you are and which ideal clients you want to attract.”  It is the introduction to the business. It is the first thing they see, even before you. So, what you do and who you do it for is important to selecting the name. The name creates an image in customers’ heads.  Do you want to be factual or do you want to create a bit of mystery?  To help with this selection you need to remember your niche market and what you do and for whom as defined earlier. Review the business specialism - what you want to be known for - and your ideal clients
 

Inspiration sources

You do not have to be factual in the name and you can get inspiration from a number of sources.  Favourite songs, places, people, films, etc., can all be sources.  Brainstorm with others for names around your values, vision, passions, your specialism, your ideal clients.  You can also get ideas from the business names your competitors or role models use.  You need to record these ideas. This can be written, but an image or sketch can be even more useful. A mood board or mind map can be helpful too. A logo idea often comes with considering a name.  You should strive to have about five good, creative names for your business to make a choice. Not all the names will be available.  There are also online business name generators that can help focus your ideas.

 

Credit: Fiverr

Check the potential names

You need to make sure of several things before you settle on the name.
 
Is the name easy to spell? 
This is important in online searches as they are the most commonly used method of finding businesses. You need to avoid quirky expressions, and names with common variations (e.g., is it Mc, Mac or M’)
 
Is it easy to say? 
Almost as important as spelling is being able to pronounce the name in different dialects or languages. This is a worthwhile consideration as exemplified in car model names.
 
Is the name easy to remember? 
This goes together with the verbalisation of the name.  If it is easy to say, it probably is easy to remember and so be searched for without difficulty. 
 
What is it in other languages?
Try to ensure your name does not mean something offensive in another language.  Even if you are not operating internationally (just now), your name will be visible throughout the world.
 
Future proof your name
This is harder than it sounds, but you want the business name to be acceptable in a generation’s time.  This means that you avoid names that are “now”.
 
Check your name for legality 
Companies House in the UK gives a list of sensitive and prohibited words on its website.  This is most useful even if you do not intend to register with them. It helps you avoid current and future difficulties in a business name. There are equivalents in other countries.  Is the name the same - or nearly so - as a registered trademark? There is more information about registered trademarks on the Intellectual Property Office website (a UK resource).
 
Check to see if the name is already in use
You can use google to check on the existence of the name as a business one.  The Companies House website also has a free facility to check on name conflicts of registered companies. Check to see if your proposed business name is available as a web address. Also check on Facebook, Twitter, and other social media sites.  It is best to have the same name and address across all the web and social media sites.
 

You may, of course, revert to some form of your name for the business name, but running through these considerations can make sure you have considered all the options for an appealing and flexible business name

Accuracy in Following the Cartoon

A question arose on Facebook that resolved itself around the need (or not) to accurately follow the cartoon. The question itself was whether a pictured piece should be re-cut. It was a relatively complicated piece, which in its current state left two significant gaps between the glass and the cartoon line.

The vast majority of responses, was along the lines of don’t worry, just adjust the neighbouring pieces to fill the gaps. (“enjoy yourself” was another theme).

To follow the majority view - make adjustments in other pieces to allow the problem piece to fit - encourages bodge. It does not encourage development in the skills of the craft. It does not encourage long term enjoyment. It pushes improvement well into the future.

The cartoon is the design in line form. Its purpose is to control the construction of the piece. It is important to follow the cartoon to express the design. This means striving to cut and fit the glass to the cartoon as accurately as possible. Line is important in stained glass, as everyone knows. If the glass is not fitted accurately, the lines will not flow according the cartoon and the design.

This is not to say the cartoon cannot be modified. It is important to look at the cartoon in detail once you have been attracted by a design. You need to look at each piece and determine its difficulty. Can I cut it? Is the design overly complicated? How might I modify the cartoon to make easier to cut pieces, and still maintain the overall design? Ensure the cartoon is drawn with accurately thin lines for the form of the craft – copper foil or leaded glass, and fused glass.  Revise your cartoon to respond to the answers to this review of it.

Whatever method you use to score and break your glass, fit the piece to the cartoon as accurately as possible to avoid excess work later. The grinder is there to make fine adjustments to the cut piece so it will fit the cartoon.  If the glass fits snugly within the cartoon lines, there should be little, or no, alteration required to the cartoon during the rest of the construction.

This is not about the methods you use during the construction of a piece.  That is open to many approaches to achieve the same end. It is about an approach to the craft.  In particular, it is about how the cartoon is used to guide the work.  If the detail of the cartoon is optional, the final result may vary from the original conception significantly.

Craft development is about striving to perform the actions as accurately as possible throughout the work. The increased skill level that this develops, provides long-term enjoyment.  And each completed piece will give a feeling of accomplishment.

 

Hake brushes

Hake (ha-kay) brushes are made from goat's hair. Their advantage over other brushes for applying kiln wash is that they hold a lot of liquid. Proper ones made from joined bamboo work better than the ones with flat handles.

Traditional Japanese hake brush

People often note that these brushes tend to shed hairs. The solution to stray hairs (given to me in a Bullseye workshop) is to invert the new brush and apply super glue at the point where the hairs emerge from the handle.  This holds the hairs in place. It will work on flat handles too.

Inexpensive goat's hair brushes of the hake style.
As can be seen by comparison, there are fewer hairs in these.

Kiln wash application with a brush

Kiln wash is applied thinly in a 1:5 powder to water mix to shelves and moulds.  The object is to get a complete coverage with a smooth surface. 

To ensure full coverage painting four coats is sufficient for excellent coverage.  The kiln was should be applied in four directions – horizontal, vertical, and each diagonal.  This ensures any gaps in one coat will be covered by the others. A broad brush that holds a lot of liquid provides good coverage.  A hake brush is ideal.  The brush should be held almost vertical with the ends of the bristles only touching the surface.

A traditional Japanese hake brush

There is no need to dry each coat before applying the next. It is not like painting your wall. All coats can be applied one directly after the other. No drying between coats is required.  In fact, earlier dried coats tend to make the application clumpy and streaky.

Some people advocate a fifth coat.  I don’t know what the fifth coat is for. What direction other than the four cardinal ones can there be?  It maybe it is insurance that the surface is coated evenly.  This can be checked visually.  The kiln washes used for glass are routinely coloured.  If the shelf shows unevenly through the kiln wash, a little more needs to be brushed onto the more thinly coated area.

It is possible to smooth the kiln washed surface once the kiln wash has a dusty surface – it does not have to be completely dry – you can put a piece of paper between the shelf or mould and your hand.  Gently rub the surface to get a really smooth finish to your kiln washed shelf.

 

More information:

https://glasstips.blogspot.com/2009/08/applying-kiln-wash.html

https://glasstips.blogspot.com/2009/08/smooth-kiln-wash-on-shelves.html

Vitrigraph Pots from Refractories

Many people are now buying or having made stainless steel square pots for doing stringer and murinni pulls.  This may be the best material for the purpose, but square pots can be made from other refractory materials.

Vermiculite

One material that can be used multiple times is 25mm vermuculite board.  These can be cut to a convenient size and fastened together with stainless steel or brass screws.

If you want to make a pot 100mm square and 100mm high, cut four boards 125mm square, and one 100mm square for the bottom.  This last one will need to have a hole of the desired size drilled at its centre.  A 19mm diameter hole is a medium sized hole.  Keep in mind that you cannot make it smaller, but you can make it bigger. 

Place the four larger squares around the base.  Drill pilot holes for the screws (if you don’t you will split the boards).  Two or three holes along each edge should be as much as needed for long term security. 

The screws at the left side of the box are omitted in the drawing, but are required

Alternatively, you can make the base to fit onto the bottom rather than inside.  In this case, cut the base to 150mm square and fix it to the sides with stainless steel screws from the bottom.

The screws at the left side of the box are omitted in the drawing, but are required

A disadvantage of the vermiculite is that glass sticks to it.  You can overcome this by lining the bottom and inside of the square with 2mm or 3mm fibre paper.  You cannot hammer out the residual glass without destroying the whole box. This lining will protect the surfaces, and the fibre can be removed after a firing, leaving clean sides.  This will not be as long lasting as the stainless steel pot is, but it is economical and adaptable to your specific requirements.

Refractory fibre

Another refractory material that can be used to construct square pots is 25mm refractory fibre board.  The sizes of the components are the same as for vermiculite.  This time rather than screws, you need stainless steel pins – 50mm long sewing pins are suitable.  You can also use high temperature wire, about 50mm long with a small right-angle hook at one end.

Assemble the four sides around the bottom as previously, and push the pins into the board to secure them.  You will need more pins than you did screws for the vermiculite.

As an additional securing measure, wrap the box horizontally with two bands of 0.5mm kanthal or high temperature wire and twist the ends together.  Then on two sides wrap more of the high temperature wire under the bottom and twist the ends together on the top of the two sides.  These wires do not have to be really tight.  They are there to prevent any failure of the pins.

This refractory fibre box is light weight although it will not last as long as the vermiculite one, but it is quick and easy to put together with a minimum of tools – knife, wire cutter, straight edge.  You can line this with fibre paper as for the vermiculite.

Safety note:

When working with vermiculite or refractory fibre, you should wear breathing protection and dust your clothing outside or change after the box is complete and put those clothes in the washing machine.

You can make a vitrigraph box from refractory materials rather than buying a stainless steel one.  Information on making one is given.