Only mix an amount of Cuprinol Ultra Tough Wood Filler that can be used within 10 minutes. Using a hard surface such as the plastic lid of the container or a wooden board, mix the filler and catalyst paste with a spatula or putty knife in the proportions of a golf ball size of filler to 40mm (1.5 inch) thread of catalyst paste from the tube. Mix thoroughly until no streaks remain and the colour is uniform. NB. Adding too much catalyst will cause the filler to become very hot, to dry very quickly, and affect its performance. Apply a thin coat of mixed filler to the repair, pressing well in to get good adhesion. Immediately fill in the remainder of the hole, leaving slightly proud for smoothing down. Allow to set hard, this takes about 30 minutes under normal conditions. Smooth to the required contours using sandpaper or file. The repair can then be finished with either a paint or woodstain. (A slight tackiness may occur on the surface, but this will not affect smoothing down, painting or staining). TIP: the filler will accept paints and woodstains such as Cuprinol and Dulux Trade Woodstains, although the degree to which it may show through will be influenced by the preparation, the nature and characteristics of the wood as well as the type and application of the woodstain. Try a test area to ensure satisfaction before proceeding.