Glue in Kilnforming

 

There is some general guidance on using glue in kiln forming processes.

Avoid Glue Altogether

Do not use glue of any kind if at all possible. First look at other ways of stabilising the pieces. You can place clear frit or powder around or under the unstable pieces. Of course, if you are firing to less than a contour fuse, this will show. If the pieces are rolling, you can grind a flat spot to keep them stable.

Use Minimum Amounts

Use as little as possible if there is no other way to stabilise the pieces until you get them to the kiln. Use weak glues. Dilute the glues if water based. Place only a small dot of glue at one place.

Use Care in Placing

Place the glue at the edge of the glass pieces, not underneath. This allows the glue to burn out cleanly. Placed in the centre, the glue burnout is trapped under the middle of the glass. This leaves a black mark or a big bubble.

Avoid Glue with Additives

Use no glue containing additives. Many of these additives will remain after the adhesive part of the glue has burned off. These will promote devitrification.

Some Popular Glues

PVA also known as wood glue, white glue, carpenter's glue, school glue, Elmer's glue in the US, or PVA glue. This boils at 112°C/234°F.

         

Super glue and other cyanoacrylate glues have a boiling point 54-56°C (129-133°F).

Lacquer and hair spray have boiling points around 189°C/372°F)

Aloe vera gel has an ignition point of about 232°C/450°F. So, its boiling point is even lower than CMC.

CMC (carboxymethyl cellulose) includes wallpaper paste, Vitragel and most fusing glues. These have boiling points around 260°C –270°C (500°F –518°F).

Xanthan gum is a thickener sometimes used as a kilnforming glue. It boils at 311°C/592°F.

Proprietary kilnforming glues are generally without additives and diluted from the concentrate with demineralised water. They also boil off in the same range as CMC.

All commonly available glues evaporate well below the “sticky” range of glass. You cannot rely on them to hold the glass in place until the glass tacks together with the heat.

Quickly fired glue - wet or dry - boils. Sometimes with enough force to move the glass significant distances. So, slow down the initial ramp rate.

The general observation is that if the glass will not stay in place without glue, it will move during the firing.

Glue is only useful to stabilise pieces in moving the whole assembly to the kiln. Where possible, build the piece in the kiln without glue at all.

Best of all, use no glue.