I'm trying to (reasonably) match a color. I'm using some powdered
dyes. I've made a couple of very small batches that are moving in the
right direction.

But...

These powders are very concentrated. A small amount more or less will
make a large difference. I doubt my ability to measure accurately
enough to scale up a "successful" test batch to make enough for the
whole project.

I figure I'll have to estimate a "formula" for the full batch, then
try it out repeatedly on scrap as I tweak it. When I think it's close
enough I'll apply it to the project. My question is, how big a batch
should I make? There's about 30 square feet of surface on my project.

I'm anticipating that someone will tell me I won't really know what
the color will look like until the test pieces dry. That brings up my
second question: How long will the dye solution be usable after it is
mixed? Hours? Weeks? Months?

Thanks in advance.

Greg Guarino