Monday, 9 May 2011

Bowed Glass for Cabinets

This is glass which is slightly convex and normally found in multiple-paned cabinet doors. Glass workers are sometimes asked by antiques dealers to do a replacement.

You can make a mould and do a slump.

However, you should consider doing a drop out or aperture drop. Normally these are thought of as circular, but they can be of any shape you want. The reason for making them as a drop out is that the surface of the bent glass will be completely unmarked.

I have made these several times for antique dealers. To do it, make a rectangle in fibre board about 10mm larger than the glazing size. Place a piece of glass about 40mm larger than the rectangular hole and fire. You need to watch. It will begin to slump at around 520C - or less if it is not float glass. You need to go slowly so the glass does not drop too much.

You will know from the existing pieces how deep a drop is required. Measure that and place a witness to determine when the slump has gone far enough. This can be a piece of kiln furniture with fibre paper over it. It can be a reference point on the far side of the kiln. In my case it normally is a stack of fibre board pieces with fibre paper on top to build it up to the correct height.

When the glass is just about to touch the witness, flash cool the kiln to just above the annealing point and close the kiln. If the temperature rises back into the forming temperature range, flash cool again. Twice should be sufficient to ensure that the glass does not move any further.