It has taken forever, but I have finally got the maple leaf design tablecloth into mordant. As per my education at earthues, I use alum acetate for cotton, which is aluminum refined with acetic acid. It works better on cellulose and has the added benefit of needing only cool water, which means I can wax before I mordant. Aluminum acetate is not poisonous, but it is so fine that a mask is a good idea. First I weigh the cloth (actually I weighed my tablecloth before I waxed it and wrote the weight on the hem in waterproof marker). I weigh in grams and my scale is accurate to one hundreth of a gram.
Alum acetate is measured at 5% on the weight of the goods, so this tablecloth needs a little over 20 grams.
Next, I thoroughly dissolve the alum in boiling water. Some dyes don't like water that hot, but alum is okay.
Finally, the dissolved alum is added to enough water to cover the tablecloth, and the cloth is immersed. Leaving it in overnight is enough, but more time does help. Since I am on such a leisurely schedule with this, I plan to leave the cloth in the mordant for a week, stirring as often as I pass by.
A sad note: the helicopters were looking for a young woman who was diving between our rocks and the little island just off shore. She disappeared that morning and has not been found. My heart goes out to her family.