welding shade numbers

Can anyone tell me whether the welding shade scale is linear, or whether it's
something else? I was wondering if #3 flash goggles under a #10 hood equal a
#13 filter, or if it's something less.
Thanks,
Mike
Reply to
Mike Vande Weghe
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Take a look at this site for recommendations:
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The article suggests looking at a bare light bulb to determine the proper shade. One thing to remember is that the goggles and the hood do not cover the same areas. Parts of your face outside the goggles will only receive #10 filtering since the goggle does not cover them. As cheap as fixed shade hood lenses are, I would not attempt to combine them.
Mike Vande Weghe wrote:
Reply to
IBM5081
I think I am able to answer my own question after studying a table from ISO 4850:1979. It looks like for each step up in filter number, the max UV and luminous transmittance each decrease by 1/3, and the max IR drops by 1/2. But you really have to have the values in each band shown in the table to be able to calculate combinations. For instance, two #3 filters would equal a #6 for UV, a #4 for luminous, a #6.5 for near IR, and a #8 for mid IR.
As for the goggle/hood combo, a #3 plus a #10 is equivalent to a #13.5 UV, a #11.4 luminous, a #13 near IR, and a #15 mid IR.
For these two examples, at least, the luminous filtering really suffers when you try to stack up filters, so the arc will appear brighter than it should.
The full table is reproduced at the bottom of this page:
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Mike
Reply to
Mike Vande Weghe
Yeah, the fixed shade lenses are cheap but I haven't been able to find the deeper shades (13 and up) from my regular suppliers (McMaster-Carr, MSC, Grainger, local welding store). I'm only TIG'ing with 120 amps, but it's on shiny aluminum and even with a #12 I can feel the effect on my eyes afterwards. Does anyone else use the darker filters on AL? I guess I'll keep looking for other sources for lenses.
Mike
IBM5081 wrote:
Reply to
Mike Vande Weghe
OK, I promise this will be my last post on this topic!
Because the scale is geometric, adding flash goggles always has the same effect, so here's all you have to remember:
If you wear #3 flash goggles under your helmet, you get a 1 step increase in visible protection, 3 steps IR, and 3 steps UV.
If you wear #5 flash goggles, you get 3 steps visible, 5 steps IR, and 5 steps UV.
That's it.
Mike
Reply to
Mike Vande Weghe
Thanks for the information.
Dan
Reply to
dcaster

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