Shaping a new mask

I have a nose mask that I had shaped using boiling water and ice water. This was a method recommended by the manufacturer. I've misplaced the brochure that explained how to do this and I wanted to use this method to try to better shape a full face mask that I am now attempting to use.

Has anyone here used this method and if so can you please post exactly how it's done?

I've been trying for over a year to find something that works for me and am very frustrated. The full face mask seems to work for me but it puts pressure on my lower gum and I wake up with my lower teeth in pain.

Some masks do have the boiling to shape instructions and some masks boiling might damage the mask. Only certain masks have the boiling to alter fit instructions.

Which full face mask are you wanting to modify?