Thin Glass Uses

• Thin glass is often used in jewelery as it allows more layers of differing colours to be built up. It also is very useful when building a channel in the piece.
• Thin glass allows more layers to be built up before going over the 6-7mm when the glass begins to expand due to the height overcoming the surface tension of the glass.
• This also allows colours that are not present in the manufacturer's palette through combinations made from two or more colours.
• Thin glass versions of dense colours provide a lighter tone which can fit in well with other lighter colours.
• Thin glasses are also useful in tack fusing, as the height is not so great and so can be used over 6mm thicknesses without adding greatly to the volume.

Seams on the Edges of Jewellery Pieces

Sometimes the edges of pieces can show the places where the glass layers join.

This happens when there is not enough heat to completely fuse the pieces together, as in a tack fuse.

It can happen to only some pieces, due to differences in temperature within the kiln. If this occurs take note of the cool spots, or better yet, run a test for the cool areas of your kiln as in this Bullseye Tech Note.  Then avoid those areas for full fused items.

If you run your kiln as fast as it will go, you can be left with seams at the sides if you do not soak for long enough at the top temperature. I usually try to achieve my desired results with a 10 minute soak. Going slower to top temperature can give you fully formed edges at a lower temperature.

You can also get visible seams if you are using iridescent glass, mica, metal or other inclusions that come to or near the edge of the piece. The solutions are to move the inclusions further in from the edges. With iridescent glass, you should remove two or three millimetres of the iridescence to allow the glass to stick together.

If you want to conceal the layers of colour used to build up the piece, you can cut your top piece - assuming it is not clear – 3mm larger all around. This allows the top layer to fold over and enclose the whole piece, concealing the different colour layers.

Fire Polishing Jewellery

Sometimes jewellery pieces come out of the kiln with imperfections that need to be ground away.

You can do a quick shaping on the conventional grinder and then fire polish. However, you will not get a fire polish at a low enough temperature to avoid distorting the piece. The way to get a fire polished surface or edge is to make the edge less rough before putting the glass into the kiln.

After you shape the pieces on the grinder, make sure you scrub them well to remove any particles created by the grinding process. Dry them and then cover the rough areas with a white paint marker. This will indicate when you have removed the scratches caused by the previous rougher grinding.

Get out your wet and dry sandpapers. Start with the most coarse (about 200) and work the ground area until the paint has been removed. Keep the sandpaper and the area being worked damp. When all the white paint has been sanded away, wash, dry, paint and go to the the next finer grit. Repeat this with progressively finer grits – normally use the grit number twice the previous grit (larger numbers indicate finer grits).

Normally, going down to 400 or 600 grit will be enough to enable a fire polish at a low enough temperature to avoid distortion of your piece. This heat range will be at a low temperature tack fuse.

This smoothing process does not take very long and is much cheaper than buying several finer grinding bits - most grinder bits are 60 to 80 grit, although it is possible to get bits up to 600 grit.

Channels for Jewellery

There are many ways to attach jewellery to the wearer.

One of these is to create a channel in the glass to allow a chain or jump ring to be placed through the piece. This is done by stacking the glass around a narrow strip of thick fibre paper – 2mm or 3mm – thick enough to allow the chain or wire to pass through.

Channel formed with 2 layers and fibre paper

This can be built with layers of thin fusing glass. These are normally 1.5mm to 2mm thick. Volume control is important, as enough thickness of glass is required to stop it contracting. The piece might be constructed with a 3mm base, and several thin layers to make a total thickness of 6mmm to 9mm.

For the channel, cut a narrow piece of thin layer about 6mm to 8mm for the top. Then cut another short enough to leave a channel of the desired width. Fill that channel with fibre paper. Then continue to build the upper layers. These layers should be around 6mm to keep the glass around the channel from drawing in.

Pendant formed in the manner described above

Mini anniversary

I've just noted that it is five years since starting the Glass Tips blog.
And this is the 600th entry.

Installing Your New Kiln

You have your new kiln unwrapped. Now where to put it?

First read the manufacturer's recommendations. If you are still uncertain there are a number of things you should think about.

One of these is getting access around it. You need to be able to work around three sides ideally if it is a top loader, two sides for smaller kilns is usually enough. If it is a front loading kiln you only really need to consider the space in front of the kiln. You are going to be carrying pieces, even shelves to the kiln so you need enough space for you and the shelf in front of the kiln. At the sides you only really need enough space for yourself.

Getting access is part of the consideration of distances from other things. Often people are worried about the heat that the kiln will be giving off. Kilns are well insulated to reduce the costs of firing, so the heat release is slow. Still, you want at least 300mm space from anything inflammable.

You also will want to think about the support surfaces. Sometimes the kilns come with their own stands, but usually these are to raise the kiln to working height. You may want to protect against any (unlikely) meltdowns, so you should put the kiln on steel, ceramic or concrete surfaces. There are a number of table top models and in these cases a large ceramic tile or ceramic fibre insulation under the kiln is an entirely adequate safety precaution.

You will need a place to put things down just before loading the kiln, so placing the kiln near adequate flat surfaces is important.

You also should think about putting the kiln out of the main traffic areas of the studio to avoid disturbance to the kiln or the rest of the studio activity.

Now that you have the ideal location for the kiln you have only begun.

You need to make sure the kiln is as level as possible. The first stage of this is to make sure the casing is relatively level. Use of a spirit level on the top front and sides is probably enough. Put hard spacers under the legs to level things up. You can if you want, level the internal base of the kiln instead of the casing. Many find that more re-assuring. Then you need to put the kiln furniture to hold up the kiln shelf into the kiln and the shelf on top of that. This is the part that really needs to be level. Spend time on it. Place pieces of ceramic fibre under the shelf supports as required to get things really level. A circle or three-way level is good for this purpose. The shelf needs to remain level to get good, consistent results. Any time you move the kiln, the shelf, or the supports, you need to check the level of the shelf.

Once you have the shelf level you are ready to do a test fire. Normally you need to have a firing without anything in it to burn out binders used in the making of the kiln. There is no reason that you cannot have the furniture (shelf and supports) in the kiln for this first firing as they need to be test fired too. In addition you can run a test to discover where the cool spots are in your kiln (every kiln has them). Look up and follow this technical note on how to run a test for discovering how even the heat is within your kiln.

Once you have run your test firing, you will want to protect the kiln floor from any spills of hot glass and the glass from sticking to your furniture. If the manufacturer has given you some kiln wash with the kiln mix it up about 1 part powder to 5 parts water and lightly paint the floor of the kiln - not the walls. The kiln furniture needs this too as does the shelf. This note on applying kiln wash will give you information on how to do it. 

It is important that you have some protective gear to do the work with kilns. At first and for fusing temperatures, you need eye protection and gloves. You need to look frequently and briefly into the kiln to monitor the firings, especially at the start of your career. For this you need eye protection. Sun glasses will not do as you need protection against infrared rather than UV light. There are a number of things that will do from welders' goggles to special lenses as used by bead makers. Use them! Every time. You will need gloves, at the start leather gloves with sleeves going half way up your forearm (such as welders' gloves) will do. Later and for higher temperature work you will need better and much more expensive gloves, sleeves, and body protection.

These things will get you off to a good start.

Brown Ceramic Fibre Paper and Board

A frequent concern about fibre board and fibre paper that appears brown when peeking into the kiln is that something has gone wrong.

Ceramic fibre papers and boards have organic binders that have to burn out during the firing. What starts as white later turns brown as the binders are burning out – often the smell is like burning paper. As the binders burn away, the fibre paper or board returns to its original colour.

The amount of smell or smoke is dependent on the amount of ceramic fibre you have in the kiln. If you have a thick board, you should think of venting the room, as there will be a lot of smoke.

Also if you are firing a large piece of glass, you should think of firing the binders out of the ceramic fibre before placing the glass on top. If you do not, the binders may not fully burn out, leaving marks of the smoke fired into your glass.

Colour “theory”

You will need to decide which colours combine well, whether they are toning, harmonious or complimentary.  By getting to grips with the rules of colour, you can give your work a unity of concept.

Primary colours

Primary colours are three key colours - red, blue and yellow. They cannot be made from any other colour.

Secondary colours

If you mix equal amounts of the primary colours, you get the secondary colours - purple, green and orange.

red + yellow = orange
red + blue = purple
blue + yellow = green

Tertiary colours

If you mix a primary with a secondary colour, in a ratio of 2:1, you get a tertiary colour. red-orange, blue-green etc.

Colour wheel example

Cool versus hot

Look at the colour wheel and you will see the left hand side of the colours are 'warm' or 'hot' and the ones on the right are 'cool' or 'cold'. This is useful when you want to create a mood in a particular room or need to make your space cosier or lighter.

Neutrals

Neutrals are one of the easiest groups of colours, or non-colours to work with. They don't appear on the colour wheel and include Black, Grey, White and sometimes Brown and Beige. They all go together and can be layered and mixed and matched. No neutral colour will try to dominate over another.

Accent colours

An accent colour is a colour used in quite small quantities to lift or to add punch to a colour scheme. An accent colour should be in a complementary colour. It works best if it's a bright, vibrant colour. Accent colours are perfect if you're concerned about using strong colour - simply add a splash of an accent colour. Keep most of your piece in shades and variations of one single harmonious colour. Then pick out just a few objects in an accent colour.

Clashing colours

Using clashing colours is thought to be inappropriate in formal settings. But in other settings they can provide drama, if they are used carefully. If they are of equal tonal strength, you can mix them together. You don't have to stop at two, you can try three or four. But if one is paler or weaker than the rest it will get lost in the overall scheme.

Sticky Labels

There are a number of products to help get the label adhesive off the glass. However you need to make sure you get the product residues off the glass before firing.

A simple and usually effective method is pull label off, use white spirit or turpentine substitutes with a plastic kitchen scrubber or fine brass wire brush to remove the adhesive. Then clean up with alcohol or methylated spirits, followed by good cleaning with your normal cleaning method, as here.

Why do kiln shelves break?

Kiln shelves are made of clay – a very hard clay, sometimes called mullite. So when firing you need to remember that like other ceramic materials it can be heat shocked.

examples of broken shelves

The recommendation is that you put the shelf on supports to keep it above the base of the kiln and allow air to circulate around both the top and bottom of the shelf.

The question remains, why do the shelves break. There are at least two reasons: physical impact and thermal shock. It is possible to knock the shelf while moving it around the studio. This impact does not always cause a break, but sometimes creates a stress point that later can develop into a crack and break. You can sometimes see the start of the crack from the edge of the shelf. In this case, you can either continue to use the shelf with support under the crack or dispose of it immediately, because at some point during a firing it will separate.

The thermal shock that causes the break occurs because (usually) uneven cooling. It seems the shelves are pretty resistant to rapid heating, but less tolerant of rapid or uneven cooling. In general un-dammed fusing and using moulds elevated a little from the shelve do not create that uneven cooling.

However placing a large refractory mould directly on the shelf can promote cracking either immediately or on subsequent firings.

Broken shelf with casting moulds laded to one side 

The main culprit in any breakage seems to be large or heavy and damp refractory moulds directly on the shelf. The mould is giving off water vapour which cools the immediate area around the mould. So as the temperature rises, the covered part of the shelf stays cool, in addition to being shielded from the general heat of the kiln while the uncovered parts of the shelf rise in heat. At some point the temperature differences in the shelf are too great for its strength to resist. The solution is to remove the shelf from the kiln and place the mould, slightly raised, on the floor of the kiln. The bricks, being softer, do not react in the same way as shelves to uneven heating.

For thick fusing with dams all around, it seems best to do this on a shelf that almost fully covered with glass and dams. This promotes more even heating and cooling of the shelf than having a small part of the shelf covered. It does mean having different sized shelves, but then you may already have some of them due to the breaking of other shelves. Just cut the broken shelf to the size you want on a tile cutter.