There are several techniques for smoothing icing on a cake, and not all of them work for all varieties of icing. Test each of the methods below ahead of time to see which works best for the icing being used.
Method 1: Smooth Icing with a Hot Knife
This method for smoothing icing on a cake is almost as simple as it sounds, but requires practice and patience to get it just right.
- After the cake has been frosted, run a metal palette knife under hot tap water and gently pat dry.
- Then, gently run the knife over the surface that requires smoothing, being careful not to dig the edge of the blade into the icing or push so hard as to make dents in the frosting.
- Repeat as necessary.
Be very careful to ensure that the knife is dry before touching it to the cake. A wet knife can ruin the icing. If this smoothing technique needs to be used multiple times on the same cake, it’s best to let the cake sit in the fridge for a few minutes between attempts, in order to avoid melting or overheating the frosting.
Method 2: Waxed Paper
This method will only work with an icing recipe that “crusts”, that is, one containing meringue powder, but it is a lifesaver for decorators that have trouble smoothing with a knife.
- After the cake has been frosted, set it aside for 10-15 minutes to allow the icing time to “crust”.
- Test to see if the icing has set by gently patting its surface. If the icing feels wet or is tacky, it’s not ready yet.
- Once the frosting has set, gently place a sheet of waxed paper over the top of the cake.
- Gently run a knife overtop of the waxed paper. As with the previous technique, keep the knife flat to the surface of the paper. Press hard enough to smooth out any imperfections, but not hard enough to make ridges or dents in the frosting. For lines or deep ridges, it may be helpful to run the knife back and forth quickly, almost as though colouring.
- Lift the paper away from the cake to see if the surface is flat enough, or if more smoothing is required.
Method 3: Finger
This method is only good for smaller areas, such as filled-in sections of a design. It wouldn’t work particularly well to smooth an entire cake. As with Method 2, this will only work with an icing that crusts.
- Allow the icing to set.
- Gently test the icing to make sure that it is not tacky or wet.
- When the icing is ready, lay a finger flat to the surface of the frosting. Gently tap the finger to the icing, smoothing any imperfections.
Remember, a perfectly smooth cake surface is practically impossible to achieve and not overly desirable. A cake is not a work of perfection, after all, it is meant to be admired and then eaten! With some practice, however, it is possible to achieve an icing surface that is mostly smooth.
Besides knowing how to smooth a cake, a good decorator knows how to find the “front” of the cake, and can strategically place decorations to hide the inevitable flaws in the icing’s surface.
