I started brewing two batches of iron and vinegar stains for my pistols, about 18 months ago. Both were made by saturating the vinegar with degreased liberon steel wool. The vinegar used was lab. grade acetic acid. With one batch I used 7% vinegar (pickling strength) in the other 30% vinegar(full strength). Both produce copiously amounts of dark brown sludge on the bottom of the bottles. I strained both last week, through a coffee filter.
Results:
Fluid color
7% vinegar:The fluid is almost colorless with a very slight red tinge.
30% vinegar: The fluid is a dark burgundy red.
Tested on maple.
7% vinegar: Nice red/brown color, with blurry stripes. The red brown color developed after drying for 2 hours. A second coat gave a uniform red brown color with poor striping.
30% vinegar: Wood turned dark green at once. After 2 hours, greygreen with pronounced stripping. Color did not change after 24 hours of drying.
A second coat gave a very dark Brown color with distinct striping and no red tones.
Diluting the stain with water did not produce red tones. Neither did diluting with with 7% vinegar and heating it to 800C for 4 hours.
What I'm looking for is a red brown color with distinct striping. I'll post pictures next week when I've finished my exams
Best regards
Rolfkt