Thank you so much for your replies! I must admit my brain is not firing on all cylinders these days, and I had not even thought about doing a sample! I have since done one, and it worked fine. The water I washed it in got cloudy, but the Fabri-Solvy washed out well, and so did the toner ink.
Fortunately, the blocks are only 16" square, so it would not ruin a whole quilt, but the blocks are complicated, which is why I need the Fabri-Solvy (at least for me!). Due to my less-than-acceptable first attempts, I know I will have at least 1 16" block I can wash just to make sure.
Thanks again!