Cooking wheat starch paste in small batches
Wheat starch paste is the quiet workhorse of the bindery. It is reversible with moisture, it does not yellow the way many synthetic adhesives do, and it costs almost nothing. The only real downside is that it spoils, so I stopped cooking large pots and moved to small batches that last a week.
The ratio
I use one part starch to five parts distilled water by volume for general work, and thin it further with cold water as I go. For tissue repairs I take it down to something closer to single cream.
| Use | Starch | Water |
|---|---|---|
| Pasting spines, hinges | 1 tbsp | 5 tbsp |
| Paper repair with tissue | 1 tbsp | 8 tbsp |
| Mixed with PVA for covers | 1 tbsp | 4 tbsp |
Microwave method
- Whisk the starch into cold water in a glass jug until there are no lumps.
- Heat for 30 seconds, stir, and repeat. After two or three rounds it turns from milky to translucent.
- Keep going in 15-second bursts until it is glossy and holds a soft peak.
- Cover the surface with cling film to stop a skin forming, and let it cool completely.
Why strain it twice
Paste that looks smooth in the jug often hides small gelled lumps, and those lumps show through thin paper as tiny bumps. Pushing it through a fine sieve once when cool, and again just before use, takes a minute and saves a lot of frustration.
If the paste smells sour or has separated into water and gel, it is done. Throw it out and cook another batch.
Stored in a clean jar in the fridge, a batch lasts me five to seven days. Let it come back to room temperature before using it on anything important.