Hot-Melt Adhesive

Some people have begun using glue guns to stabilise their glass before transporting to the kiln.  These use glue sticks which are a hot melt adhesive.

Hot melt adhesive, or hot glue, is a form of thermoplastic.  It is commonly sold in solid cylindrical sticks of various diameters designed to be applied using a hot glue gun. The gun uses a heating element to melt the plastic glue. The glue is tacky when hot, and solidifies in a few seconds to a minute. The glue squeezed out of the heated nozzle is initially hot enough to burn and even blister skin.

The glue sticks are available in a variety of melt temperatures.  The standard and most commonly available glue sticks are white to cream in colour and the guns have an orange applicator.  The hot glue is delivered from non-adjustable guns at about 195°C.  This is hot enough to burn skin and the possibility of heat shocking the glass should be considered.

3M make a low temperature variety of hot melt adhesive which needs low temperature glue guns – the 3M version is blue, and the sticks contain LT as the suffix to the part number.  This is applied at 129°C.  This is still hot enough to burn skin, but possibly with less risk of thermal shock to the glass.

The risks of breaking the glass from the heat of the glue is one of the risks.   The greater risk is of the effects of the thermo plastic on the surface of the glass.  The glue is a plastic. All of us who have left a plastic item in the kiln can witness to the black smoke created.  So, it won’t do your kiln much good, and will require firing empty to burn out all of the plastic residue. 

It also will not do you glass much good.  The thermo plastic melts and will vaporise at some (unknown) temperature.  But it will leave a residue for the process of devitrification to develop.

My recommendation is to avoid the use of hot melt adhesives for anything going into the kiln.  It is most likely to cause difficulties with the kiln and the glass.