Thursday, 5 February 2009

Cutting with Patterns or Templates

As a general rule, always make the hardest cut first. Glass tends to run in a straight line. This means inside curves should be done before any other cut is made.

It will be most efficient to place the pattern to be cut with the inside curve facing the raw edge of the glass. If something goes wrong, the pattern can be backed away and tried again, resulting in less glass and time wasted.

It is also hard to break very thin strips of glass away from the desired piece without getting ragged, chipped edges. Allow a 6 mm minimum distance from the edge of the glass when placing the pattern on the glass unless the edge is going to be used for the whole edge of the piece.

When scoring around a paper pattern it is necessary to steer (turn) the cutter in the proper direction. The paper will not turn the cutter for you. You should steer the cutter by turning your upper body rather than your fingers, wrist or elbow.  Failing to do this may allow the cutter to run over the pattern and so fail to score the glass.

Alternatives to using the paper pattern directly as a guide in cutting glass are to outline the pattern paper on the glass with a pen or to draw the pattern on the glass while it overlays the drawing. You follow the inside edge of the pen line with the cutter.

Directly cutting the glass over the cartoon avoids the time spent in making patterns, and the difficulties and inaccuracies in multiple transfers of the shape. Often a light source is required under the cartoon to enable the lines to be seen through the glass. There will always be times when the glass is so dark or opalescent that the lines cannot be seen and therefore a pattern is required.

Keep the pattern cutting restricted to the times when nothing else will do.

The only times I use patterns for cutting are when the glass is too dense for the cartoon lines to be seen through the glass with light behind or for repeat shapes where a pattern can speed the process.

Two pattern pieces used to draw repeats of sails on the glass and then cut out

A boat design assembled in the kiln
 I draw around the pattern pieces, as that avoids the possibility of the cutter riding up on the card that I use for templates.  This comes from several occasions when the cutter did go over the template which prevented the score and so created a bad break.  Others do score around the template stuck to the glass successfully.