Why chocolate seizes
A little water dissolves sugar surfaces and glues them together. A lot of water dissolves the sugar completely. The danger zone is in between.
If you read nothing else
Seizing is sugar particles wetted just enough to stick together. Adding a tablespoon of boiling liquid per 100g dissolves them fully and gives a sauce — which is a different product, not a repaired one.
The mechanism
Melted chocolate is a suspension: solid sugar and cocoa particles dispersed in liquid fat. Sugar is hydrophilic and the fat is not, so the two phases coexist happily as long as no water is present.
Introduce a small quantity and the water wets the surfaces of the sugar particles, dissolving them slightly. Those tacky surfaces bind to each other and the suspension collapses into a stiff, grainy paste. It is closer to wet sand clumping than to anything about the chocolate itself changing.
Why more water fixes it
The counterintuitive part follows directly. If a small amount of water creates tacky sugar bridges, enough water dissolves the sugar completely — and the mass becomes a smooth chocolate sauce.
About a tablespoon of boiling liquid per 100g does it. What you have afterwards is a sauce and not melted chocolate: it will not temper, will not coat and will not set hard. Ganache works on exactly this principle, which is why a ganache made deliberately never seizes.
Where the water comes from
Rarely from anywhere obvious. The usual sources are steam escaping around a bain-marie bowl, condensation dripping from a lid, a spoon that was rinsed and not dried, and water- or alcohol-based flavour extracts.
That last one catches people repeatedly: vanilla extract is mostly alcohol and water, and adding it to melted chocolate seizes the batch. Oil-based flavourings exist specifically for this reason.
Covered in this guide
- Chocolate has seizedThe rescue procedure.
- Melting in a double boilerThe melting method most likely to introduce the water in the first place.
- Infusing flavour into chocolateHow to add flavour without adding water.
Sources
- ChocolateHQ editorial synthesis — ChocolateHQ(citation identity confirmed; passage not re-read)
- The Science of Chocolate — Royal Society of Chemistry(citation identity confirmed; passage not re-read)