Since I have recently started stiffening some of my crochet projects, I thought it would be interesting to compare some common methods to see what is best and how they differ. I used Berroco Comfort DK to make the test pieces. I crocheted single crochet circles, submerged one circle into each mixture, and placed them over glass bowls to dry.
1. GLUE METHOD: (2 parts Elmers Glue, 2 parts water). Mix glue and water together until thoroughly blended.
In my test, this sample yielded the stiffest result, but altered the look of the yarn the most. I would only use it on a very light color. I like that you could change the ratio of glue to water and control the stiffness.
2. SUGAR METHOD: (2 parts sugar, 1 part water). Bring sugar and water to a boil, then watch until it turns clear. Remove from heat and allow to cool.
3. CORNSTARCH METHOD: (1 cup + 1 TBS water, and 3 heaping teaspoons of cornstarch). Dissolve starch in 1 tablespoon of water. Boil 1 cup of water, then reduce heat and add starch, stirring until thickened. Keep stirring until it is the consistency of pudding. Allow to cool.
This method turned out about as stiff as the sugar method. It made the yarn a lighter color, so I think it would work best with light colored yarn.
To sum up, I think the best method, look and stiffness wise, is the sugar method. If you need a very stiff result, the glue method seems to be the stiffest. Depending on what you have on hand to use, I think all of them work fine, but you may have to adjust the ratios to get the level of stiffness you are looking for. Next time I am in the US, I will try some of the commercially available stiffeners such as Mod podge or Aleene's, to compare!