Fondant
One word for two different substances — a crystallised sugar syrup and a kneaded sugar dough — which is why the advice a reader finds so often does not match the thing in front of them.
What makes it set
Sugar crystallising, and Sugar drying out
A baked product is set by the oven. This one is not — and what sets it instead decides almost everything that can go wrong with it. See the whole family by mechanism.
Also called sugarpaste (UK) — The rolled kind specifically. Not the poured kind., rolled fondant (INTERNATIONAL), ready to roll icing (UK), poured fondant (INTERNATIONAL) — The crystallised syrup. A different substance from the rolled kind., fondant icing (UK)
Two preparations share this name and they are not versions of each other.
POURED FONDANT is a sugar syrup boiled, cooled without being disturbed, and then worked hard as it cools further. The working is the point: it forces the supersaturated syrup to crystallise while the crystals are still microscopic, and a mass of very fine crystals reads as opaque, white and smooth rather than as sugar. Warmed gently it pours; cooled it sets firm with a shine. This is the glaze on a mille-feuille and inside a fondant fancy.
ROLLED FONDANT, which most people now mean, is not crystallised at all. It is icing sugar kneaded with glucose or glycerine and usually a setting agent, into a pliable dough that can be rolled thin and draped over a cake. It never sets hard in the middle. It dries at the surface and stays plastic underneath, which is what lets a covered cake be cut without shattering.
Almost every confusing piece of advice about fondant comes from the two being treated as one. Graininess is a real fault of the poured kind and essentially meaningless for the rolled kind; cracking is a real fault of the rolled kind and not a thing the poured kind does.
What holds it together
Poured fondant is a dense suspension of very fine sucrose crystals in a saturated syrup — the crystal size, not the composition, is what makes it smooth. Rolled fondant is a sugar-and-humectant dough held plastic by glucose or glycerine, which is why it dries only at the surface.
A statement of what each preparation is. The claim that crystal size rather than composition determines perceived smoothness is the standard confectionery account and is recorded here as definitional rather than measured, because BakeHQ publishes no crystal size figures.
RecordedTrue by definition rather than by measurement
What temperature does to it
Poured fondant is worked warm and sets as it cools; overheating it dissolves the fine crystals and it sets coarse and dull instead. Rolled fondant is barely temperature-sensitive on its own and extremely sensitive to what temperature does to the air around it: sugar is hygroscopic, and a cold covered cake brought into a warm room collects condensation on its surface, which dissolves the outermost sugar into a sticky film. That is what people mean by fondant sweating, and it is a dew point problem rather than a fault in the icing.
Follows from sugar's hygroscopicity together with ordinary condensation. No figures are given because the point at which it happens depends on the room, not on the fondant.
RecordedFollows from evidence recorded elsewhere on BakeHQ
How it keeps
Rolled fondant keeps for months sealed airtight at room temperature and is ruined by the fridge, which both dries it in the cold air and wets it on the way out. A cake covered in it keeps at cool room temperature; refrigerating one and then serving it is the single commonest way to arrive at a sticky, streaked finish.
RecordedEstablished practice, not a measured result
What a good one is like
- Texture
- Rolled: pliable and smooth, with no dry edges or surface cracking. Poured: opaque and satin, with no perceptible grain
- Structure
- Rolled: thin enough to drape without tearing, thick enough not to show what is underneath
Where it stops
Rolled fondant is a covering rather than a filling and it does very little for flavour; almost every cake underneath it needs a layer of something else between the two, both for taste and because fondant applied directly to a moist crumb dissolves into it. It will not survive a refrigerated display case, or a marquee in August, or a long car journey in either. And it cannot be made to set hard: readers looking for a surface they can pipe fine detail onto want royal icing over the top of it, not a different fondant.
Why it cracks, and why rolling it thicker is usually wrong
Cracking in rolled fondant has three separable causes and they need different corrections.
SURFACE DRYING. Fondant loses water from whatever face is exposed. Left uncovered while the cake is levelled, the top skins over, and the skin has none of the plasticity of the material under it — so the moment it is stretched over a corner it splits. This is why it is kneaded, rolled and lifted without pauses, and why any resting happens under wrap.
TOO MUCH ICING SUGAR ON THE BENCH. Every dusting adds dry sugar to the surface and takes it further from the ratio that made it pliable. A little cornflour, or a non-stick mat, does the same job without changing the material.
THE CAKE MOVING UNDERNEATH. A cake that is still settling, or that was covered while warm, shrinks and shifts under a covering that cannot shrink with it. That produces cracking at the shoulder rather than randomly, which is how it is told apart from the other two.
Rolling it thicker helps only with the third, and makes the first worse by increasing the weight that has to stretch over the edge.
Related
Things that go wrong
Fondant is cracking, sticky or sweating
Losing water and gaining it are opposite faults of the same covering, and the corrections are the reverse of each other.
Used on and in
The traditional covering, over marzipan — the marzipan is there partly to stop the cake's moisture reaching the sugar.
What it is built from
In poured fondant it interferes with crystal growth so the crystals stay fine; in rolled fondant it holds water so the paste stays pliable.
Commonly confused with
Both are sugar coverings and they set by different routes — one crystallises or stays plastic, the other dries rigid — so advice written for either is wrong about the other.
Keep reading
Buttercream
Sets by solid fat rather than by sugar crystallising, which is why the same complaint means something different in each.
Fondant is cracking, sticky or sweating
Work through what you can actually observe, rather than a list of possibilities.
Fillings, icings and creams
The whole family, grouped by what sets each one.