What happens if watercolour paper fails to stretch?

If the paper fails to stretch you can reuse it by cutting it off the board and going through the soaking and stretching process again. There are four faults that are the most common reasons for failure when stretching paper:

• The paper has not soaked long enough. It looks flat when dry but still cockles when painted on. Running paper under the tap will not be sufficient to soak it.
• Gummed paper tape, which is sometimes difficult to find, has been replaced with masking tape or brown sticky tape. These don’t stick and they don’t stretch with the paper.
• Too wet a sponge has been used to moisten the gum strip and the gum is wiped off, preventing it from sticking.
• Boards or frames have been stood upright to dry, making the water run to the bottom, pulling the paper away from the top. This is why paper stretching is difficult on studio walls.