welding lens - the outer clear one?

As long as the material is Lexan then it doesn't matter. If you can buy them for 50 cents then buy them.

Got one today, fits perfect. I recommend a plastics store to anyone tired of getting nickeled and dimed to death over proprietary-sized pieces of plastic. They cut it while I waited.

GWE

The TAP Plastics store near me has a bin full of remnants. I just buy a piece for a buck and cut it with a sheet-rock knife--score and snap. But, I don't know whether it is Lexan. Ernie, is that important (and why?)

I'm not Ernie, but I know that polycarbonate is much harder and thus more difficult to scratch than e.g. acrylic.

GWE

Lexan (polycarbonate) naturally blocks a lot of UV, and is shatterproof. Acrylic shatters and doesn't block UV.

"Ernie Leimkuhler" wrote: Lexan (polycarbonate) naturally blocks a lot of UV, and is shatterproof.

^^^^^^^^^^^^^^^^^ Thanks. I see that Lexan is better, but doesn't the welding filter block UV?

Actually Grant, polycarbonate is softer and scratches easier that acrylic. It is shatter resistant though. In fact, 1/8" Lexan will stop a .22 long rifle slug fired at practically point blank range. I know because I actually made the tests. Not in the lab, but in the woods. ERS

Wow, my optometrist lied to me.

So who was wearing the safety glasses and let you point a .22 rifle into their eye? Must *really* have been a believer .. :-)

Eric, are you having your pig roast this year? Or equivalent?

Grant

Hmmm. I'd be interested to see the evidence that acrylic doesn't block UV. I was taught a uni that just about every plastic is a strong absorber of UV. Do you have a source for this Ernie?

Cheers Glenn

for one. There are also specially transmissive acrylics too,

Steve

I really have no knowledge about this, but if you look at the pdf on that site:

about page 6 they have graphs for a few materials. They include general purpose acrylic and polycarbonate. Looks to me like general purpose acrylic blocks a little more UV than polycarb.

I would think that on a helmet the main lens ought to block UV by itself. I wouldn't expect the outer shield to be important. From a strength and safety factor I guess polycarb should win, but I doubt if the UV factor really matters.

Yes Grant. The first saturday in august. Always the first saturday. This year that happens to be the 5th. I think. You and Yours gonna make it? I hope so. Your optometrist may have been thinking of polycarbonate with the anti-scratch coating. I've got some 1/8 lexan if you want a piece. Eric

Whether the outside protection lens absorbed UV or IR is not important; the filter lens will do that.The outside protection lens is to prevent welding spatter getting on the filter.CR39 material is often chosen because welding spatter adheres to it less than plain glass.Other plastics are often chosen on a cost basis.--Gwyn