Icing, frosting, glaze, fondant: what the words mean

ICING and FROSTING are largely the same word in different places. British recipes say icing; American ones more often say frosting, and where American usage distinguishes them it tends to mean thin-and-setting by icing and thick-and-spreadable by frosting. BakeHQ treats them as the same category and says which kind it means.\n\nThe genuinely different things are underneath those words, and they are told apart by WHAT HOLDS THEM TOGETHER.\n\nFAT-BASED. Buttercreams of every kind. Sugar suspended in, or dissolved into, a fat that is soft at room temperature. Holds its shape because the fat is solid; softens when warm.\n\nSUGAR-AND-WATER. Glacé icing and glazes. Sugar dissolved in a little liquid, setting as the liquid leaves. Thin, glossy, and it sets hard rather than staying soft.\n\nEGG-WHITE-AND-SUGAR. Royal icing, and the meringue family. Sets to a genuinely hard, brittle finish because the protein sets alongside the drying sugar. This is why it is the piping icing.\n\nSUGAR PASTE. Fondant. A pliable dough of sugar with something to keep it plastic, rolled rather than spread. Structurally closer to a confection than to an icing.

This is the payoff, and it is the reason the classification is worth reading rather than memorising.\n\nA FAT-BASED ICING fails on temperature and emulsion. Too warm and it slumps; too cold and it will not spread; and the fat can break away from the liquid entirely, giving a curdled, split appearance that no amount of extra sugar corrects.\n\nA SUGAR-AND-WATER ICING fails on ratio and on drying. Too thin and it runs off; too thick and it will not level; and it stays tacky in humid conditions because what makes it set is water leaving.\n\nAN EGG-WHITE ICING fails on foam damage and on sugar. Fat contamination destabilises it, overbeating drives water out of the protein network, and sugar that never dissolved leaves it gritty.\n\nFONDANT fails on moisture and handling. It cracks when too dry and tears when too wet, and it dissolves where it meets a wet surface underneath — which is why it is not applied straight onto a moist cake.\n\nSo the first diagnostic question about any icing fault is which of the four you have.

It is worth separating because the corrections point in opposite directions and the wrong one makes it worse.\n\nHARD, CRYSTALLINE GRIT is undissolved sugar. Caster or granulated sugar used where icing sugar was needed, or a cooked icing not held long enough for the crystals to go into solution. It needs finer sugar, more liquid, or more time.\n\nSOFT, CURDLED GRAININESS is a broken fat emulsion — the fat has separated from the water it was holding. It needs the temperature corrected and more beating, and adding liquid makes it worse.\n\nRub a little between finger and thumb. Sugar is sharp and does not disappear; a split emulsion is soft and smears.

This is a reference on how icings behave, not on how to decorate with them. Piping technique, colour work, modelling and the visual craft of cake decorating are a genuine discipline and they are not what this site is for.\n\nThe line is roughly where the question stops being about material behaviour and starts being about design. Why royal icing sets hard is here; how to pipe a rose is not.