No, knot filler does not sink when it is applied correctly. hence, when you shoot the Knot Filler into the repair, let it cool down for a while, before you cut off the excess part, you will see a perfect repair. One of the big advantages with Knot Filler is that it does not sink over time. Knot filler might expand a bit in warm temperatures, whereas it might shrink a bit in cold temperatures when it is first applied. From our experience, the reaction mostly occurs in large-size repairs and does not occur in standard repairs. Another advantage of knot filler is that you can see the result of your repair instantly. It will not change character or sink later on the surface where it is applied.