Hi Alan,

Bobby Rockwell here. Rande is correct, but crackling was also a deliberate part of a decoration used on Acid Etchings and other thick walled pieces such as sculptured Rose quartz. The acid etched vase (right) in you picture is an example of this. The other cintra vase am not so sure of because of the angle prevents me from really seeing it.

Hi Alan,

Would like to add that the Greek Key (right picture) may be on a base of Rose Quartz whick was crackle like the Rose Quartz stone.

Beth Shaut

Co-Efficient of Expansion–Not Enough

In response to Rande Bly

His explanation is partially correct. Combining glasses is very tricky.

At Orient & Flume Art Glass we melted from batch 7 colors in our furnaces. Every morning we had to make the test by putting 2 colors together and pulling them into a long thread. It was not to see if they crack. The test was to see if the thread stays straight or curves. If it curves the glasses don’t have the same co-efficient of expansion. One is compressing the other.

Then we found out we had to do another test to determine the softening point. Co-efficient of expansion test was not enough. We took 2 rods of the same diameter, one of each glass and mounted them in a kiln to test if one softened much before the other.

If both tests were ok then we could put the glasses together safely.

Shari Maxson Hopper