This is curious, "The adhesive dries to a very thin even layer and is easily reversible with cold water. It is non-staining and does not become brittle upon ageing. Other applications in this section might include temporary facings, mends or backings. If you can use hot water for a wash bath, you might like to use MC as the temporary adhesive as it will not dissolve in hot water but is easily reversed in cold water. "
This specifically applies to methylcellulose, whereas sodium carboxy methylcellulose (CMC gum) is soluble in either hot or cold water.