Quick Icing
Make a paste of confectioner's sugar and cold water until of the proper consistency to spread. The proportions can not be given, as the absorptive quality of the sugar varies. This icing should not be used on a cake that will stand long before being served.
A water icing, the simplest of all cake coverings, and the one most sensitive to proportion. The original declines to give quantities for good reason, but a working starting point helps.
- A starting ratioAbout 1 cup of confectioner's sugar to roughly 1 tablespoon of cold water gives a stiff spreading paste; a little more loosens it to a pourable glaze. Add the liquid a few drops at a time, since the difference between thick and runny is very small.
- Why proportions varyEstes is right that absorptive quality differs. Modern confectioner's sugar contains 2-4 percent cornstarch as an anti-caking agent, which takes up water differently from sugar milled without it, and any sugar that has sat in a humid kitchen will need less liquid.
- Sift firstPowdered sugar compacts into lumps in the bag, and lumps will not dissolve in cold water at this ratio. Sift or whisk it before adding liquid or the icing will be gritty.
- Cold water, not warmWarm water dissolves more of the sugar and tends to give a thinner, more translucent result that can soak into the crumb. Cold water keeps the mixture a stiffer, paler paste.
- The hinge: use it at onceA water icing sets by evaporation only, forming a thin crust while the interior stays soft. Left to stand, it pulls moisture from the cake beneath, goes dull, cracks along the edges and can weep. Spread it and serve the cake the same day.
- The cake must be coldOn a warm cake the icing thins, slides off the sides and lifts crumbs into itself. Let the cake cool completely first.
- Variations that hold upSubstituting lemon juice, milk or cream for part of the water is period-standard and gives more flavour and a slightly softer set. A drop or two of vanilla is enough for a cup of sugar.
- YieldOne cup of sugar makes roughly enough to cover the top of an 8- or 9-inch layer; double it for a top and sides.
This comes from Good Things to Eat, as Suggested by Rufus (1911), written by Rufus Estes, who was born enslaved in Tennessee in 1857 and went on to cook for the Pullman Company's private railcars and later for the subsidiaries of United States Steel in Chicago. His is among the earliest cookbooks published by an African American author, and its terse, professional entries reflect a working chef rather than a domestic-science instructor: no coaxing, no explanation, just the fact that the sugar's behaviour cannot be predicted and the cook must judge it. Water icing of this kind seems to have served as a common alternative to boiled or royal icing, which demanded a sugar thermometer or long beating with egg white; a plain paste of powdered sugar and water asked nothing but a bowl and a spoon, and it closely resembles the glaze still poured over doughnuts and bundt cakes. Estes's warning about standing time is the sort of detail that separates a hotel and railcar kitchen from a home one, where a cake was iced when it was wanted rather than hours in advance.