What is the Difference between Hydrocal and Plaster of Paris?

Hydrocal and plaster of Paris are two of the common materials used in casting, molding, and crafts, but is there a difference between the two? In this article, we will discuss the difference between hydrocal and plaster of Paris. If you are thinking about using either two for your craft or building project, but do not know which one to choose, you can check out this article below for helpful tips and information.

What is the difference between hydrocal and plaster of Paris? The difference between hydrocal and plaster of Paris is that hydrocal is stronger. As compared to plaster of Paris, hydrocal takes a lot more details and they do not slough off so you do not have to deal with lots of dust and chips.

What is hydrocal? How do you prepare hydrocal? What is plaster of Paris? How do you prepare plaster of Paris? These are some of the questions that we will discuss in this article. Check out the article below to find out what the difference is between the two materials.

What is the difference between Hydrocal and plaster of Paris
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What is Hydrocal?

Hydrocal is versatile gypsum cement that is great if you are doing a solid and hollow casting of figurines and lamp bases. It is made for thin sections and is also more durable so there is minimal breakage during mold removal. Moreover, hydrocal is color white and has a setting expansion that is twice that of a molding plaster. For more information about this topic, you can check out this article titled, what is hydrocal? We have shared an in-depth discussion.

How Do You Use Hydrocal?

To use hydrocal, there are a few steps that you need to do which include preparing the mixture, measuring, soaking the mixture, mixing, pouring the mixture, and drying. Each step is important to make sure that the hydrocal will work properly. Let us learn more about these steps below.

Preparing the Mix

The first thing that you need to do is to prepare the mix. You need to use water at temperatures between 70 and 100° Fahrenheit. Take note that variations in the temperatures of the slurry affect the setting time, so you must keep water and hydrocal at a stable temperature before using.


The next step that you need to do is to measure the ingredients. Weigh the water and hydrocal according to the consistency that you need. The ratio of the two ingredients is important because it affects the physical properties of the cast piece.


Once you have measured the ingredients, you need to soak them. You need to slowly and evenly sift hydrocal into the water. Avoid directly pouring hydrocal into the water. You need to let it soak for about one to two minutes. Make sure that the hydrocal is completely dispersed in water before mixing.


Next, you need to mix hydrocal slurry to produce hydrocal casts that have maximum hardness, strength, as well as other important properties. You can mechanically mix hydrocal by batch and continuous processes. We have also shared this article that discusses what happens if plaster of Paris gets wet. You can check out the article for useful tips and ideas that you can refer to when working with plaster of Paris.


The next step is to pour the mixture. You need to be careful in pouring the slurry to prevent air entrainment and also to have a uniform and smooth surface. Make sure that the slurry is carefully poured into the deepest area. This is to make sure that the slurry evenly flows across the surface of the mold. Bear in mind that when you pour a large amount of slurry directly on the mold, it results in slight densification of the cast.


The last step is drying. All casts must be dried as quickly as possible so that they can develop maximum physical properties. Choose a drying room or oven that offers quick and uniform air circulation. Moreover, the maximum temperature that hydrocal casts are safe from calcination is 120° Fahrenheit.

✅ Video – Casting Hydrocal White into a Plaster Mold

Kc Bodycasting shared the video below on YouTube. It shows how to cast shydrocal white into a plaster mold with the use of a fiberglass mat. If you are wondering how hydrocal is used to create casts, you can check out the video below for the process.

What is Plaster of Paris?

Plaster of Paris is a gypsum plaster that quickly sets. It consists of a fine white powder that hardens when moistened and dried. It is used for crafting as well as a construction material. They are easy to use and durable.

How Do You Use Plaster of Paris?

Plaster of Paris is an ideal material to use for craft and sculpture projects. Moreover, they are easy to prepare and can be set after just a few minutes. It is easy to mix plaster of Paris, but there are vital steps that you need to consider so that you can have a solid and durable sculpture. Let us learn more about this below.


The first step is measuring. You need to cover the work area using newspapers. Use a mixing container that can fit the amount of mixture that you will make. When it comes to plaster of Paris, the ideal mixing ratio is two parts plaster powder and one part water. Make sure to break up any lumps that form in the mixture using a spoon.


Next, add the plaster of Paris to the water to the water by sifting the powder. Avoid pouring all the powder into the water. After sifting the powder, do not start mixing yet. You first need to tap the side of the container to disperse the powder and also to remove air bubbles. Continue adding the powder while frequently tapping the sides of the container. Stop when the powder is almost covering the surface of the water. You can also check out this article that discusses if plaster of Paris is flammable. We have shared an in-depth discussion about the topic.


The next step is mixing. Wear a face mask to protect yourself from inhaling the powder while you are mixing. Wearing gloves is also recommended. Stir the plaster of Paris and water mixture slowly until it forms an even and smooth consistency. Avoid mixing vigorously because it can cause air bubbles to form. Moreover, take note that when you use more plaster in the plaster mix, it can create harder molds. On the other hand, when you use less plaster, it creates more porous as well as brittle molds.


After thoroughly mixing the ingredients, you can proceed to the drying. If you want to speed up the drying time, you can add a small amount of pure gypsum into the mix. On the other hand, you should add drops of lemon juice if you want to slow the drying time. Moreover, warm water is used to speed up the setting time. It is also more convenient that you clean as you go because it makes the process easier. Do not pour any leftover plaster of Paris down the drain. They can harden and cause the pipes to clog. Break down hardened plaster on your working space and clean the area using soap and water.

What is Hydrocal Used For?

Hydrocal has many uses. For instance, it is ideal for making a hollow and solid casting of sculptures, figurines, and commercial casts. Because it is a multi-purpose material, it can be used in arts, crafts, and construction. We have also shared this article that discusses what hydrocal is made of. Check out the article for more information about the topic.

What Can I Use Instead of Plaster of Paris?

Alternatives that you can choose from if you do not want to use plaster of Paris includes mixing lime and water, soy powder and water, chalk and water, and acrylic undercoat. Choose an ingredient that you are most comfortable working with. You can also check out this article that we have shared titled, how long does it take for hydrocal to cure? We have shared tips and ideas about the topic that you can refer to.

Can You make Plaster of Paris Stronger?

You can make plaster of Paris stringer. You can do this by using a gauze bandage, glass fiber, and other suitable materials. Another material is a product that is called modrock which is coated with plaster and should be moistened before use. You can also add color to the plaster using poster paint or tempera. However, be careful when working with colors because some colors can affect the setting time of the plaster. You can also check out this article that we have shared that discusses how to make plaster of Paris stronger. We have shared tips and ideas that you can refer to.

What are the Three Types of Plaster?

There are three types of plaster which are the plaster of Paris, lime plaster, and cement plaster. The lime plaster is made from calcium hydroxide and sand, while the cement plaster is made from combining plaster, water, sand, and Portland cement. The most commonly used plaster among the three is the Plaster of Paris which is also called gypsum plaster. You can also check out this article that we have shared that discusses what the difference is between hydrocal and ultracal. We have shared an in-depth discussion about the topic.


You have reached the end of this article that discusses the difference between hydrocal and plaster and Paris. We have also shared tips and instructions on how to use hydrocal and plaster of Paris. Both have pros and cons so you need to make sure that you weigh out your options to make the best choice based on the project that you are working on. Thank you for reading!

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