I recently covered these chairs for the studio. The material that came on the chairs was not pretty and it was a synthetic which would have melted if hot glass landed on it. The replacement material is a thick 100% cotton - Like bluejeans if you get the hot glass off it quickly it is OK and much less likely to melt the chair to your leg.
I thought I'd share how I did it - Here is a "tutorial" in recovering a simple chair.
First you have to remove the old material some people like to just cover it but for these swivel chairs it would have been to bulky.
|Before OK but meltable and boring|
You will need a staple gun and the new material
Staple that bottom cover you saved
Looking good now align the screws and put it back together.
|All finished! Pull up a chair and torch a while!|