I went on Amazon and found
I went on Amazon and found Merv13 filter cloth. 16sq ft for under $20. No fiberglass. I cut small ovals and put a piece of double sided tape on the edge and stick it on the inside of my premade cloth mask. Works great.

Jim, what face velocity are

Jim, what face velocity are they rated for?  Unfortunately, they don’t always tell you that, and that number is the key to minimizing the pressure drop.  Even 0.15 i.w.c. is higher than it should be.  And the other factor is real-world performance, which depends on face velocity and the space in the return box.

Also, you’re looking at manufacturer’s data for 2 filters.  Real-world performance of a range of filters is part of the focus of those studies in the first I article I listed above.  Did you read it?

I have two identical size
I have two identical size MERV12 filtrete filters from 3M setting on my bench.
One is a 1 inch thick filter and the other is a 5 inch filter.
The 1 inch filter has a factory rating of .31 iwc at 1025cfm printed on the filter by 3M
The 5 inch version only has .15 iwc at 1025cfm printed on it by 3M

Jim, thanks for your comment.

Jim, thanks for your comment.  I always warn readers about filter pressure drop when I discuss this topic.  The thickness of the filter, however, has less to do with pressure drop than you think.  Yes, the pleats add more total area, but they aren’t always well separated.  Here’s an article I wrote on three research studies on filters:

Do High-MERV Filters Always Reduce Air Flow?

Better than filter depth is the face area of the filter (length x width).  Here’s an article I wrote on that topic:

The Path to Low Pressure Drop Across a High-MERV Filter

I’ve got three MERV-13 filters in my house and the pressure drop across all of them is less than 0.06 i.w.c.  And that’s with three months of use.

Never cascade filters because
Never cascade filters because the accumulative restriction on the system will be too great.
A MERV 8 carbon filter will provide more than enough dust and allergen filtering and it will filter out dozens of toxic gasses that will pass right thru a MERV 13 filter.

Buy washing an alcohol you
Buy washing an alcohol you very well might be creating some funky weird strange chemicals unless you’re just washing cotton so I would just use sunlight to disinfect them even that might break down high Merv filters somewhat and release unintended perhaps dangerous chemical outgassing a activated charcoal filter high Merv might be your best bet between you and whatever other exotic type chemical action you got going on

increasing a filter to a
increasing a filter to a higher MERV may increase the delta P across the filter. Suppose you put the higher MERV in series downstream of a lower MERV rating, will that help the delta P across the filtration in total?

Brad, you ought to read some

Brad Young, you ought to read some of my other articles, this one in particular:

Do High-MERV Filters Always Reduce Air Flow?