méthylcellulose is a water retainer for paints and coatings. it is used at too high temperatures or on too porous supports, it allows to extend the working time. it is also used as a resin to make gouaches and in acrylic and vinyl resins for the preparation of colors.
preparation: take 1 L of lukewarm water, add 1 drop of liquid black soap, add slowly, quickly turning 10 g of retainer, let swell for 1 hour then stir again for 1 minute, the retainer is ready, you can filter it if you have lumps left. It is used at a rate of 1 to 3% of the weight of the lime + load, if the support is porous or if it is too hot.