How to Model With Hydrocal

Modelers cast diorama features such as hills and rocks from Hydrocal.

Artists and hobbyists use Hydrocal, a type of gypsum plaster, to cast small objects such as statuettes, lamp bases and scenery for model railroads or wargames. Hydrocal comes in a variety of types, but the most common is Hydrocal White, a powder mixed with water to create a strong cement. Casting items using Hydrocal is a good way to produce durable objects, which you can then sand, paint and decorate.

Things You'll Need

• Mold
• Water
• Dish detergent
• Toothbrush
• Spray bottle
• Hydrocal powder
• Bucket or large bowl
• Mixing stick

Instructions

1. Prepare your mold. This can be a commercial latex, plastic or plaster mold, or one made from your own model. Clean the mold, first rinsing it with water and then washing with a mixture of half detergent and half water, carefully scrubbing at corners and edges. A clean mold will reduce the likelihood of air bubbles in the casting. Spray the mold with water from a spray bottle, then shake off any remaining drops.

2. Pour Hydrocal into a mixing bowl or pail and add water, following the proportions on the packaging. The exact ration of water to plaster will vary, but it is usually around two parts plaster to one part water. Stir the mixture steadily with your stirring stick to create a smooth, even consistency.

3. Tap the sides and bottom of the mixing bucket or bowl firmly to dislodge air bubbles.

4. Pour the mixture into the molds. Pour promptly before the Hydrocal begins to set.

5. Vibrate the molds to release more air bubbles by tapping the sides of the mold or the surface they are resting on.

6. Wait for the Hydrocal to set. Depending on the exact mix of plaster, setting time can vary, but it is usually around 15 to 20 minutes.

7. Remove the completed casting from the mold.

Tips & Warnings

• Clean your bucket or mixing bowl after every mix to make sure the Hydrocal doesn't set inside it.

• You can make mixing easier by using an electric mixer. Again, make sure to clean it thoroughly.

• Hydrocal casting can be messy. Use drop cloths and wear old clothes.

References

• C. C. Crow: Casting Hydrocal