I had that problem too. A year or two back, I opened my tub, and when I looked in, I saw mold growing in patches in various spots. Threw that out and just last month I went out and got a new tub after using lightweight spackle, which I will not switch back to again (expensive stuff, and it dents very easily). All I could find was similar looking tubs of Elmer's Wood Filler so I figured it was good enough. When I used it, it seemed like the same stuff and it sanded down just fine. It's not bad, but I can't really compare it to FnF because I really can't remember its characteristics compared to what I have now.

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Josh
NAR #87993