David Weaver
for fast drying poly 550 - probably about 39% (which would agree with the 58% figure for mineral spirits plus a couple of percent of other hazardous items).

That would leave a guess of 100-69.7-3 or thereabouts for the wipe on type. 27.3%.

If one adds half of the volume in mineral spirits, the solids content of the homemade wipe on would be 39/150 = 26% (close to the guess of the wipe on type).

100% would give 39/200= 19.5%

In the scheme of woodworking, i'm kind of wondering what we're saving exactly. I understand the implications with a production shop, but I have to admit that if I still have my poly can, I haven't used the first quart. If I used poly, I'd probably use two or three quarts a year. I calculate a potential savings based on all of these assumptions of about 13% if buying the mineral spirits by the quart, and 23% if buying by the gallon. I know it'll shock some, but mineral spirits aren't something I keep on hand.

It does look like there's potential savings if performance is seemingly the same. It also looks like folks who thin it 1 to 1 and who think they're really saving are just working with fewer solids than the pre-mixed product.