What Happens if Plaster of Paris Gets Wet?

Are you planning to use plaster of Paris to make sculptures for your garden, but are wondering what will happen when it gets wet? Many people are using plaster of Paris for outdoor decorations and also to cover their exterior walls. Plaster of Paris makes wonderful sculptures that will enhance the look of your outdoor yard or garden. But what happens if they get wet? We will discuss the answer below.

What happens if plaster of Paris gets wet? When plaster of Paris gets wet, it will absorb water that falls on its surface. The reason for this is that plaster of Paris is a very porous material when it is dry. Hence, water easily gets absorbed. Fortunately, you can waterproof the plaster of Paris by filling in its surface.

Plaster of Paris is a material that is used in various applications. It is used for building construction, crafts, and casting. They are used to create plaster statues that you can display in your gardens. However, constant exposure to moisture and humidity can cause plaster of Paris to degrade. As time goes by, they will start to chip and get damaged Check out the rest of the article below for more information.

What happens if plaster of Paris gets wet
Photo by Julia Volk from Pexels

What If Walls Covered by Plaster of Paris Gets Wet?

If your walls are covered with plaster of Paris gets and it gets wet, it can get damage depending on the amount of water that it is exposed to. Plaster of Paris is used in both interior and exterior walls. They have many benefits and are also easy to apply. However, they are vulnerable to water, moisture, and humidity. Let us learn more below about what happens to plaster of Paris when it gets wet according to the amount of water that it is exposed to.

Small Water Exposure

If plaster of Paris is exposed to a small amount of water like a splash from the garden hose or when a wet item rubs against the walls, you do not have to worry much because it will not damage the plaster wall. Make sure to wipe off the water from the wall using a dry cloth or sponge.

Large Water Exposure

If your plastered walls are exposed to a large amount of water, it can cause the plaster to soften and it will start to get loose especially if it is unattended for a long time. Usually, this type of water damage is caused by leaks from drains or pipes. After long exposure, molds can grow in the damp walls which can also put the health of the occupants at risk. Take note that the longer the plaster of Paris is exposed to water, the more damage it will have.

Exposure to Water Saturation

Water can cause the plaster of Paris to get damaged making it softer and more volatile; it can also damage the inside of the walls. Walls that are saturated with water can cause the wood lath behind the plaster to expand. When the lath starts to expand, it will push outward and can cause the walls to crack. When this happens, you might need to change your wall depending on how large the crack is.

Do You Need to Replace Damaged Plaster of Paris Walls?

You might need to replace damaged plaster of Paris walls if it is beyond repair. If you do not want to install a new plaster wall, you can choose to tear out the wall with the use of pry bars and use a modern drywall. Wear the necessary protection when tearing out the walls like face masks and goggles. Also, if you are working indoors, open the windows and doors so that there is proper ventilation.

✅ Video – Easily Repair Damaged Plaster

ElectronicsNmore shared the video below on YouTube. It shows how to easily repair damaged plaster.  In the video, how to damaged plaster cast items are shown. You can check out the video below to watch the step-by-step guide.

Is Plaster of Paris Waterproof?

Plaster of Paris is not waterproof. However, you can make it waterproof by mixing other materials into it. Take note that plaster of Paris is a dry and porous substance so it will absorb water when it gets wet. To make it waterproof, you can coat it with a primer. After that, paint it with extension paint. If you want it to have a natural look and would rather not paint it, you can coat it with linseed oil. For better absorption, make sure to sand the surface of the plaster before you apply the linseed oil.

Can You Waterproof Plaster of Paris?

Plaster of Paris can be waterproofed. Waterproofing is done by filling out the porous surface of the plaster. There are many fillers that are used to waterproof the plaster of Paris. This includes wax, resin, and shellac. Each of these filler works differently. Moreover, bear in mind that you cannot perfectly waterproof the plaster of Paris and there is a probability that water can still get through the surface. However, waterproofing gives them an extra layer of protection from water, humidity, and moisture. You can also check out this article titled, how to make plaster of Paris stronger? We have shared tips and ideas on how to make plaster of Paris less prone to breakage and more durable.

How Do You Make Plaster of Paris Waterproof?

There are some steps that you need to do to make plaster of Paris waterproof. You need to make sure that the plaster is completely dry before you start waterproofing. Learn about these steps below.

Step 1 – Regardless you have a plaster of Paris sculpture or walls, make sure that it is completely dry thoroughly before you start waterproofing.

Step 2 – Clean and wipe the plaster to remove any dirt or debris. Then coat it with your preferred waterproofing agent. Next, allow it to thoroughly dry.

Step 3 – Repeat adding the waterproofing agent if needed and let it dry. Once it is completely dried, you will have a waterproof plaster.

Step 4 – If you want, you can paint the plaster of Paris once it is waterproofed. Allow the paint to dry.

Step 5 – The last step is to spray the entire plaster of Paris with a clear sealer to protect the paint. Allow sealer to dry.

Do You Need to Seal Plaster of Paris?

You need to seal the plaster of Paris if you are planning to place it outdoors. Also, you need to sea, it before painting. It is vital to seal the plaster of Paris before painting to make sure that the paint will not get absorbed by the plaster. It is also easier to paint the plaster once you have sealed it.

What Can I Use to Seal Plaster of Paris?

To seal the plaster of Paris, you can coat its surface using acrylic paint. The acrylic paint will provide a consistent gloss on the plaster to make the paint look more stunning. Since plaster of Paris is porous, make sure that you seal it thoroughly especially if you will use it outdoors.

How to Seal Plaster of Paris

One way to seal the plaster of Paris is to use linseed oil. This is a good sealing agent that you can use if you do not want to paint the plaster but would like to provide it with a barrier from humidity and moisture. Below are the steps on how to seal plaster of Paris that you can refer to.


Before adding the sealing agent, you first need to sand the surface of the plaster. Sand the plaster until it is smooth and even. Sanding makes the surface more absorbent for the sealing agent.

Apply Linseed Oil

The next step is to apply linseed oil. Use a high-quality brush so that you will have an even coating. Brush a light coat of linseed oil over the surface of the plaster of Paris. Make sure that you apply the oil little by little or you will end up with a greasy plaster surface. The oil will easily sink into the porous surface of the plaster. Be careful when working with linseed oil because it is flammable. Wash the brush and container that you used with water to remove the oil before storing them. 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.

How Long Does Plaster of Paris Take to Dry?

Plaster of Paris can set in just a few minutes. However, allow it to rest for about an hour or more into the mold before removing it. Plaster of Paris takes about 24 to 48 hours to completely cure. It is an ideal material that you can use for castings and other art projects because it is easy to use and is widely available.

Will Plaster of Paris Dissolve in Rain?

Plaster of Paris will not dissolve in the rain once they have dried and completely set. On the other hand, constant rain exposure can cause the plaster to soften, crack, loose, and get damaged. This is especially true if it is not waterproofed. We have also written this article titled, is plaster of Paris is hard? We have shared an in-depth discussion about the topic.

What Happens When You Add Water To Plaster Of Paris?

When you add water to plaster of Paris and water, both undergo a chemical change. As the particles rearrange, a new substance is formed.


You have reached the end of this article that discusses what happens when plaster of Paris gets wet. We have found out that the plaster of Paris is porous and can easily get damaged when wet. The good thing is that you can make it waterproof by sealing it. You can refer to the steps above on how to seal and waterproof plaster of Paris. Thank you for reading!

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