Duh! Now I remember why I call spring allergy months "stupid season"!!!! Last night I used a masking fluid to mask some areas on a new canvas painting. I hadn't used masking fluid on canvas before, only on watercolour paper--and it's been ages since I used it at all. Worked well on the canvas. Then I tried to wash my brush. Grrrrrrr!!!! I forgot to dip it in dish washing liquid before I used it. Great experiment with masker on canvas=one ruined acrylic brush. And stupid season for me lasts till after ragweed season. Sigh.