Is Hydrocal Stronger than Plaster of Paris?


This article discusses if hydrocal is stronger than plaster of Paris. Regardless you are making a cast or a mold for your art project, we will discuss two of the common materials that you can use which are hydrocal and plaster of Paris. Both are plaster but have their differences. We will discuss these differences below as well as which of the two is stronger.

Is Hydrocal stronger than plaster of Paris? Hydrocal is stronger as compared to plaster of Paris. Aside from that, hydrocal also takes more detail and does not slough off. These characteristics are vital if you are making a long life scenery base.

Most of the time, we choose a material for the project that we are working thinking that it is an excellent choice, only to find out in the end that the material is not the correct one. Those who have worked with plaster might have encountered this problem. To help you get started, we will discuss two of the common plasters used which are hydrocal and plaster of Paris. Check out the rest of the article below for more tips and ideas.

What is Hydrocal?

Hydrocal White is versatile gypsum cement that is an excellent choice for making solid and hollow castings. This material is specially designed for making thin sections. Hydrocal has excellent strength which helps lessen breakage when the plaster cast is removed from the mold.

Is Hydrocal Better than Plaster of Paris?

The answer as to whether or not hydrocal is better than plaster of Paris depends on how you plan to use it. As compared to most plasters, hydrocal is stronger. On the other hand, it is still a plaster that is heavy, dense, and can shatter when dropped. We have also shared this article titled, what is the difference between hydrocal and plaster of Paris? Check out the article to find out more about the differences between both materials. We have also shared tips and ideas for using hydrocal and plaster of Paris for your art or craft projects.

How Long Does it Take for Hydrocal to Cure?

Hydrocal can take about 24 hours or more to cure depending on how thick it is made. If you want the cast to be completely cured before you remove it from the mold, wait until it feels dry and warm. Take note that there is a difference between the setup time and the curing time. If the plaster has not thoroughly cured, it will feel cold to the touch.

However, there are instances wherein you do not want the plaster to completely dry out before it is removed from the mold. If this is the case, you should wait for at least two to three hours or longer depending on the temperature. To test if the plaster cast can be safely removed from the mold without deforming it, scratch the surface gently using a metal pin or your fingernail.

What is Plaster of Paris?

Plaster of Paris is gypsum plaster that is made from a fine white powder that hardens when it is moistened and dried. It is also a quick setting which is ideal for arts and crafts. The plaster of Paris is used since ancient times and is used in many applications. It is a high-quality, quick-setting plaster that is usually normally used with gauged lime putty. Combining both ingredients cuts the setting time shorter. Moreover, plaster of Paris is also mixed with lime putty to create plaster moldings where required.

How to Make Plaster of Paris Stronger

Adding glue to the mixture can make the plaster of Paris stronger. It is easy to do especially when you are working with small batches. Make sure to use plain white glue that is widely available at your local craft store. Below are the steps on how to make plaster of Paris stronger.

Set

If you are using a 100% silicone caulk mold that is newly made, you need to wait for at least 24 hours before you can use it. Using the mold before it is not ready will result in bubbles formation in your casts. It is ideal that you wait at least a week. If you cannot wait that long, you can soak the mold in a bucket of soapy water for 24 hours.

Mix

How you mix the plaster will affect the outcome of your cast. You need to mix the plaster carefully to avoid adding air. Bear in mind that the more you mix, the faster the plaster will set up. Mix the glue to the water and plaster mixture. It is not recommended that you add the glue to the water before adding the plaster because it can cause the plaster to clump together. Aside from that, the glue can also end up floating to the top of the mold.

Mix the plaster into the water before adding the glue. In some instances, the glue will float on top of the water. Do not worry much because it will eventually combine into the mixture.

Demolding

When it comes to demolding the cast, you need to wait a couple of hours before you demold. Let the plaster cure overnight. On the other hand, if you do not want the plaster to be a little wet so that you can easily clean it up after demolding, you can take it out as soon as it does not dent or get squished when you scrape it with a toothpick or a metal pin. Smooth out any bubbles that you can find using a skim coat of a watery mixture once it has completely dried.

How Does Plaster Work?

You can find a wide array of plaster for every kind of application. Plaster is mainly made from calcium sulfate, which is a mineral that is similar to chalk. Calcium sulfate is mined and processed.  During the process, it is ground up into a powder form and then heated. The process of heating the powder is called calcining. When heated, the calcium sulfate loses some of its water content. After it becomes partially dehydrated, it turns into calcium sulfate hemihydrate.

In this dehydrated state, it can be used as an ingredient in plaster. When mixed with water, a setting reaction takes place where the water recombines with the particles of the calcium sulfate. As this happens, it changes from hemihydrate to dihydrate. Crystals are formed in the mixture of water and calcium sulfate during the setting reaction which makes the plaster harden. Generally, the crystals form a structure in the plaster that provides it strength.

✅ Video – Materials and Process: Plaster Casting

Nasher Sculpture Center shared the video below on YouTube. It discusses the materials and process of plaster casting. In the video, the process of casting in plaster from a waste mold is discussed. Check out the video to learn more about the topic.

Is Plaster of Paris Waterproof?

Plaster of Paris is not waterproof. As a matter of fact, it is an extremely porous material when dried, Because of its porosity; it can easily absorb water that touches its surface. On the other hand, you can waterproof the plaster of Paris. Waterproofing plaster of Paris is important especially if you will use it outdoors. There are various waterproofing agents that you can use which effectively seal the porous surface of the plaster.

Does Plaster of Paris Break Easily?

Regardless of how hard to try to create a strong and hard cast from the plaster of Paris, it is still plaster that is brittle and vulnerable to breakage. As compared to plastic, plaster can easily break especially if it is dropped. Moreover, you cannot use plaster of Paris to make miniature pieces. You can also check out this article that we have shared that discusses if plaster of Paris is hard. We have shared an in-depth discussion about the topic.

How Hot Does Hydrocal Get?

Hydrocal molds can be heated at a maximum temperature of 120 °F. When exposed to a temperature that is higher than this, hydrocal will start to calcinate. You can use free water in the mold to have a higher drying temperature. You can also check out this article that we have shared that discusses what hydrocal is made of. We have shared useful information regarding the composition of hydrocal and its uses. You can check out the article for more information about the topic.

Conclusion

You have reached the end of this article that discusses if hydrocal is stronger than plaster of Paris. We have found out that hydrocal is stronger than plaster of Paris and can also take a lot of detail. We have also shared tips and ideas for both materials. Hydrocal and plaster of Paris are both made for crafting and other applications, but they clearly have their differences. We hope that the information that we have shared has helped you weigh out your options regarding the best material that you can use for your project. Thank you for reading!

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