Q: "In your article about tub repair, you say, 'But you're almost sure to be disappointed by the [do it yourself] repair job.' Is that based on functional and durability issue? Or is that simply because of color match?" The reader goes on to say that she has "an acrylic tub with a crack" in it the pan area and is considering a Bondo or patch method.
Answer: Miracle Method, the national franchise that refinishes bathtubs, says that one fault of these do-it-yourself kits is that they are epoxy-based, and that within a year or so, the epoxy will start to turn yellow. Of course, that's the opinion of a competitor, so take it with a grain of salt.
Frankly, I have heard nothing good about do it yourself shower/tub refinishing kits. I think the important point is to differentiate between "shower refinishing" and "shower repair." Refinishing is best left to the pros. But for a temporary patch job (until you can afford a bathtub refinisher or a bathrub liner), the Bondo will probably work. Besides, Bondo is fiberglass resin-based, not epoxy-based. That's the good news. The bad news is that Bondo is difficult to work with.
You will always see the repair spot, but at least it will protect the area under the shower pan from getting wet and rotting out.