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
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:
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:
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:
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
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