Wilton stuff is not really gumpaste.
Make your own using Nic Lodge's recipe. Can;t get much better
4 large egg whites
2 lb. bag of 10X powdered sugar
12 level teaspoons Tylose (#TP100)
4 teaspoons shortening (Crisco)
1. Place the egg whites in a Kitchen Aid mixer bowl, fitted with the flat paddle.
2. Turn the mixer on high speed for 10 seconds to break up the egg whites.
3. Reserve 2/3 cup of the powdered sugar and set aside.
4. Turn the mixer to the lowest speed, slowly add the remaining sugar. This will make a soft consistency royal icing.
5. Turn up the speed to setting 3 or 4 for about two minutes. During this time measure the tylose in to a small container.
6. Make sure the mixture is at the soft-peak stage. It should look shiny, like meringue and the peaks fall over. (If coloring the entire batch, add the paste
color at this stage, making it a shade darker than the desired color).
7. Turn the mixer to the slow setting and sprinkle the Tylose in over a 5 second time period. Next, turn the speed up to the high setting for a few
seconds. (This will thicken the mixture).
8. Scrape the mixture out of the bowl onto a work surface that has been sprinkles with the reserved 2/3 cup powdered sugar. Place the shortening on
your hands and knead the paste, adding enough of the powdered sugar to form a soft but not sticky dough. Usually I check by pinching with my fingers and they
should come away clean. Place the finished paste in a zip lock bag, then place the bagged pasted dough in a second bag and seal well.
9. Place in the refrigerator for 24 hours if possible before use to mature the paste.
10. Before use, remove from the refrigerator and allow the paste to come to room temperature. Take a small amount of shortening on the end of your finger
and knead this into the paste before using.
11. Always store the paste in the zip-top bags and return to the refrigerator when you are not using the paste. Will keep under refrigerator for approx. 6
months. You can keep the paste longer by freezing. Be sure to zip lock closed.
If you will be freezing a batch of paste, allow it to mature for 24 hours in the refrigerator first before placing into the freezer. I have kept the paste in the freezer for up to 3 years with no problems.