De Glue Goo, is a gel product, available at wood working stores, that is designed to put on surface glue, and remove it. You have to spread it on and let it sit, but it dissolves PVA glues readily, and as I understand it also works on Fish glue and HHG. It's mostly vinegar in a gel, and vinegar will dissolve it too, but it dries before it gets the work done, unless you wet a rag in it and put that on the glue. It will work fine for Elmers', but I don't know how you'd get the glue out of the crack after it is softened, without damaging the crack more. Elmers' like other PVA glues will not stick to itself, so if you want to re-glue it, you'll have to remove it. It's one reason to always check with a builder or repair person before doing something like that. If you don't have HHG, you can always buy a bit of Knox gelatin at the grocery, put it in a glass, with an equal amount of water, heat it, in some water, to 140*, stir it till its liquid, and, voila, hot hide glue! Use that for crack repairs, and they can always be re-glued without much in the way of clean up.
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