On 28/07/17 03:21, wrote:
On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, 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
Relevant all over again for August 21, 2017.

So based on A Norton's formula:

4 5 6 7 8 9 10 11

4 7 8 9 10 11 12 13 14
5 8 9 10 11 12 13 14 15
6 9 10 11 12 13 14 15 16
7 10 11 12 13 14 15 16 17
8 11 12 13 14 15 16 17 18
9 12 13 14 15 16 17 18 19
10 13 14 15 16 17 18 19 20
11 14 15 16 17 18 19 20 21

So the first column and row are the shades you are adding. Follow 14 on the diagonal to combine your shades. So a #10 + a #5 is #14.
If you want to check the formula the spread sheet link is:

https://docs.google.com/spreadsheets...it?usp=sharing

My neighbours borrowed a couple of my fixed shade filters when they went
on a cruise in IIRC 2015 for the Norwegian eclipse and they borrowed my
11EW filters and were very happy and many others on the cruise were
envious as the view my neighbours got of the eclipse was apparently far
superior to that through the cruise supplied cheapy filters.