When it comes to icing decorations on a cake, precise measurements and a steady hand are essential for success. The use of icing swags on a cake is a classic, elegant look that you can apply to a variety of cakes, ranging from birthdays to weddings. Though swags, also referred to as "string work," can be difficult, with enough practice you can produce perfect swag detail on just about any cake or pastry surface.
Colour your prepared royal icing. Royal icing is a thick decorator's icing that you can find premixed at local craft stores or make from a meringue powder recipe. Using your gel colours, place the desired amount of royal icing in a bowl and add one drop of gel colour at a time. Mix the colour through the icing to incorporate fully before adding more colour.
Fill a pastry bag. Add your coloured royal icing to a pastry bag and twist the top of the bag to ensure icing does not seep from the top.
Mark your cake. Using a toothpick or other pointed object, mark on the cake surface where you want the divisions of your swags to appear. If you do not want to leave toothpick marks on the cake, place the cake in front of you so that you can stand over it. At the top edge of the cake place a dot of royal icing. Directly across from that dot on the opposite top edge of the cake, place another dot. Then turn your cake so both dots are horizontal and place a third dot at the top edge of the cake. Do an opposing fourth dot of royal icing. You should now have four equally spaced markings. You can continue this method to add more spacing if needed or start Step 4.
Measure the bottom point of the swag. To do this, centre your toothpick or pastry bag between the two top edge dots. Measure from the bottom of the cake up to your knuckle as your base of the swag's arc. Mark the base of the arc with icing or your toothpick. Repeat this process with the other top edge markers until every swag has a bottom arc mark.
Begin the swag. For a straight line swag, use a slight amount of pressure to string your royal icing from the bottom swag arc marker to the top edge marker and then continue from the other side. If you're doing a beaded swag, simply apply even dots to your swag markers, working from the base of the arc to the top edge. Keep your beads evenly spaced. With both methods, create a slight arc as you go from the centre marker to the top edge marker.
When piping icing swags on a tiered cake, have the swags from each tier start in the centre arc of the top tier's swag detail. If you place your royal icing markers in the wrong space, use a cake spatula to scrap the dot off the cake's surface.