I have not done this but did find this. Hope it helps

STIFFENING SOLUTION: Use wither a hot sugar solution of one cup of sugar poiled 3 ot 4 minutes in a cup of water, or a hot starch solution of 9 level tablespoons of starch in one cup, pluse one tablespoon of water (orTO BLOCK THE PRIECES: Cool solution slightly before using. Wet crochet basket first, then dip in solution and thououghly saturate basket and handle; lightly squeeze out excess startch or syrup. Cover a flat padded surface with wax paper. Place corresponding bowl or glass upside down at center of wax paper. Stretch and shape body of basket over bowl or glass, pin last rounds. As crochet gets almost dry and begins to harden, remove pine, turn basket rightside up. With your hands, stretch and shape ruffle shape. Allow to dry completely. For additional body, when dry, using a pastry brush go over entire basket lightly with more solution, allow to dry again. Repeat until desired stiffness. To remove bowl or glass from startched basket, run a dinner knife gently between bowl and crochet.

I found the following info:

Tips To Stiffen Crocheted Projects

It's never too early to begin planning for Christmas. You may have begun creating your crocheted decorations, such as ruffled doilies, bells, snowflakes, thread baskets, and other items, which lend seasonal flair to any room, if they are finished nicely.

All of the items just mentioned have one common requirement for finishing - a stiffening solution. To help make your holiday decorating a little easier, here are some hints and various products you can use for stiffening crochet.

Before you begin, make sure that you have a form around which you can shape your piece. Flat designs require either a blocking board, an ironing board, or even a thick piece of cardboard. Baskets, angels, bells, and other three-dimensional items call for something that resembles their correct shape, like a foam ball or cone. Cover your form with plastic wrap to keep it dry, and use rust-proof pins to hold your project in place.

Now you're ready to choose which stiffening solution will work best with your particular piece. There are four primary mixes from which you can choose: sugar water, commercial starch, white glue, and commercial fabric stiffener. Each of these can be applied with a clean, soft paintbrush.

During our great-grandmothers' day, sugar water was the most popular solution. Most households had sugar on hand, so women used this method of stiffening in spite of its disadvantages. Unfortunately, sugar water tends to yellow with age, get sticky in humid conditions, and attract bugs. If, for historical accuracy, you want to use this method, mix 1/2 cup granulated sugar with 1/2 cup water, and heat to boiling. Immediately remove the liquid from the stove, and let it cool to room temperature before using.

Commercial starch is easy to use, and it preserves much better than sugar water. Follow the manufacturer's directions to mix it, and then apply the solution with a paintbrush, or for a heavier application, you can dip your project into the starch. If you dip your crochet, carefully squeeze out any excess liquid and reshape the object before letting it dry. Commercial starch will wash out, so if you want to reshape the piece after it's dry, it's only a matter of washing the piece and starting over.

White glue, another simple solution to use, will also wash out, and it's very easy to find. Just mix the glue with equal parts water and apply it. For a more pliable finish, you may want to add a little more water.

Of all the stiffening methods, commercial fabric stiffener provides the most durable finish for your projects. Keep in mind, though, that it is permanent. You should be able to find this product at your local craft store and follow the package directions for mixing.