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Sparks from electrical welding or from electrical grinding damage surfaces of glass or tiles while they do not damage the leather apron and even plastics. For example protecting glass in the old welding helmets has to be replaced frequently while the rest of the helmet, even plastic parts of it are not damaged at all. The recent helmets even do not have glass protection but use a plastic cover which does not show any damage after use.

There is probably something fundamentally different between materials which bounce back hot iron pieces (droplet) and which melt and hold hot droplets, which results in permanent damage. Crystal lattice, temperature of melting, chemical reaction, surface tension?

Michael Seifert
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Vladimir Smutny
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1 Answers1

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Building on By Symmetry's comment:

I suspect that a large part of this is due to the fact that for a piece of leather "damaged" means "has a hole in it" whereas for a glass visor it means "is too chipped to see through anymore", which will happen much sooner.

Glass is much easier to damage by a short, rapid transfer of heat than either plastic or leather. If a droplet lands on glass, it dumps heat into a small spot on the glass, which expands; since the glass around this spot is relatively unheated, the hot spot flakes off due to shear stresses. Plastic doesn't shear off due to its flexibility and in leather only a few fibers burn away, so both materials remain intact under these conditions.

Asher
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