On Thursday, August 17, 2017 at 11:05:18 AM UTC-7, wrote:
On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

It is not linear 7+7 =/= 14

Simply put S_1 + S_2 - 1 = S_true

Example if you have two shade 7s:
7+7-1=13 Not Safe

So two #10 lenses together should be fine, correct?