The mixture will foam as it boils. Stirring or whisking prevents the mixture from boiling over, burning, or forming lumps. To reduce the chance of these mishaps, make a double boiler by placing the pot of wheat paste in a larger pot containing roughly 2 cups (500 mL) boiling water. If it thickens too much to stir, add more water.
If using starch, the mixture will be translucent when ready.
If the batch isn’t sticky enough, stir in sugar or white glue. Begin with 3 Tbsp (50 mL) sugar or glue and add more if necessary. To preserve the mixture longer and deter bugs from eating it, mix in a small amount of copper sulphate. [3] X Research source
Each brand of flour and starch is a little different, so the exact consistency will vary. As long as there are no lumps it should work well. To remove lumps from the paste, strain it through a thin sieve or pair of tights. [4] X Research source
Reheat unused paste in a covered container after each project to sterilize it. [6] X Research source Pour a little water on top of the paste for storage. If the paste is cool the water will sit on top of the paste and prevent mold from reaching it. Pour out the water again before using.
Remove any lumps from the paste to prevent bubbles and lumps from tearing the poster. Attaching posters to other people’s property or in public places is illegal in some regions.
For very large posters or high surfaces, a push broom may be useful.
If you used whole wheat flour, the paste may have brown flecks or tinge. Apply such paste lightly to avoid obscuring the poster. If you don’t have enough time or paste to cover the entire poster, prioritize the corners or furthest edges.
Some bookbinders recommend using starch powder rather than flour to create a more transparent paste.
