Avoiding Grinding Lines

 

Sometimes in a completed piece a grey line appears between pieces or at the edge of the whole piece. Most often these are the result of grinding the edges to fit with each other, which leads to devitrification.

In scoring and breaking glass to fit into a fusing project, there are often adjustments needed to the pieces for a good fit, so processes need to be used to minimise grinding.

The obvious preventive is accuracy in scoring and breaking to get a good fit without adjustments. This reduces the need for changing the shape.

Many people use their grinders to make the adjustments required though. Most grinders use a medium or coarse grinder bit. This leaves many pits in the edges of the glass, requiring a significant amount of cleaning to remove glass dust from them. The general practice is to place any ground piece immediately into water to avoid the glass particles drying into the pits. This is rarely sufficient to avoid devitrification, because the surface of the edges are not smooth, enabling devitrification to grow on those rough areas.

Fine grinding heads are available and should be used when adjusting sizes for kilnforming. These need to be cleaned just as for the coarser grits. The results of grinding with a fine grit bit (or to 400 grit with other tools) is usually enough when clean to avoid devitrification.

Another way to eliminate the appearance of grinding lines is to avoid grinding altogether. If adjustments are necessary, groze the glass to shape. The slight irregularities will be accommodated by the movement of the glass during contour and full fuses. Larger spaces between glass can be filled with powder of the same colour. If the joint has different colours, use the powder of the darker or denser colour as it will fill the gaps with less evidence.