Sunday, 3 June 2018

Home Made Devitrification sprays

You can buy a number of devitrification sprays. Some of them are lead bearing and will not be suitable for food and drink containers. Many times people apply them before firing the first time to prevent devitrification. More often these sprays are applied after a piece has become devitrified. However it is applied, these sprays are not cheap.

borax in powder form

It is possible to make your own devitrification solution. It is made from borax which you can buy from your local chemicals supplier, or sometimes as a washing powder – but make sure it has no additives! 

An example of a borax washing powder

 To make a solution, boil a few cups of water. Take the water off the boil and put in 4 – 5 tablespoons of borax. Stir and allow to stand until cool. Pour off the clear liquid and you have a saturated solution of borax. The sediment in the bottom can be added to more hot water to make more of the borax solution.  You will have to break up the remaining crystals of borax to enable suspension in the hot water.

Add a couple of drops of washing up liquid to the solution. This is enough to break the solution's surface tension. It helps to give an even distribution of the solution across the clean glass by reducing the surface tension and therefore, beading of the liquid that otherwise occurs.

You can spray this solution onto the glass, just as the commercial sprays.  Or you can brush it on as you do kiln wash on a shelf.  It requires an even application to ensure there are no streaks left on the finished glass. 

This works because borax is one of the fluxes used in glass making to reduce the melting temperature of glass batch and so serves to soften the surface of the glass enough to overcome mild devitrification.

Revised June 2018