Plaster can be quite a hassle to work with, especially when it ends up getting too hard for you to work with before you even finish working on your wall. It can get frustrating when you realize you’ve made a mistake and want to fix it but can’t because the plaster is already too dry to work with. Having plaster that sets a bit slower will make it easier to apply for the average DIYer.
Here are ways to stop plaster from drying too fast:
- Mix it with cold water
- Use other types of plaster
- Add a bit more water
- Apply a thicker coating of plaster
- Choose the right time of the year
- Use a primer
- Wait for rain
- Spray water on your wall
- Wet your tools between applications
Why Does Plaster Dry Too Quickly?
Plaster can dry too quickly based on various factors such as temperature, low humidity, the material of your wall/ceiling, and the plaster mixture itself. On average, plaster fully dries in around 2-3 days, but it sets in place around 30 minutes after application.
For a quick chemistry refresher, water dries up because of evaporation. Evaporation happens because of how heat and water interact with each other. As water temperature rises, the movement of water molecules causes them to go into the air. You’ll notice this by observing hot water releasing steam or how boiling water creates bubbles.
Having plaster that dries too quickly will leave you with a weaker finish that is much more susceptible to damage. Water, in both plaster and other mixes, starts a process called hydration.
Hydration, to put it simply, allows the gypsum in your plaster to crystalize and bond together. The bonding due to crystallization is the reason why your plaster goes from gooey to hard.
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How Do You Stop Plaster From Drying Too Quickly?
As we’ve mentioned, many things can cause plaster to dry too quickly. As a good rule of thumb, you should treat plaster as if it’s a finish that you can’t change again later on. You need to be careful and pay attention as you apply it to your wall.
With that said, there are times when your plaster can dry up too quickly for you to make any proper finishing touches.
We’ve got you covered, and here are different ways that you can stop your plaster from drying too quickly:
1. Cold Water for the Mix
It’s a staple tip to always mix plaster with water that is cold and clean. The water temperature will not affect the chemical composition of your application at all, only its setting time.
The molecules in colder water move a lot less than room temperature, implying that it will take more energy for the molecules to move enough to evaporate.
The water also needs to be clean, as any solid particles in the mixture will end up causing the plaster to dry faster.
2. Use Other Types of Plaster
Aside from gypsum plaster, you can also explore other options such as lime plaster or cement plaster. These types of plasters are much harder to work with but also have a much longer setting time. Lime plaster takes around two weeks to dry, while cement plaster takes about five days to cure fully.
3. Adding a Bit More Water
As we mentioned earlier, having a plaster mixture that is too thick is a sign that there is a lack of water, which is something that we don’t want.
REMEMBER: The general rule of thumb for plaster is using a 1:1 ratio of plaster to water, but if you’re going to extend the drying time, you can opt to just add a bit more, around a 5% increase, of water.
4. Apply a Thicker Coating of Plaster
Applying a thicker coating of plaster onto your wall will increase its setting time. Note that we are referring to the thickness of the application to the wall and not the consistency of the plaster itself.
Once you’ve applied plaster to a wall, you can opt to backtrack to where you first skimmed through your wall and put an additional amount of plaster to that area you’ve just covered.
5. Choosing the Right Time of the Year
Choosing to apply plaster during the wintertime will cause it to dry slower because of the lower temperatures. You will need to make sure that the temperature is not too low, below 40 degrees Farenheight, as it can cause the water in your plaster to end up freezing.
6. Using a Primer
If your wall is made out of a porous material that absorbs water, such as wood, then adding a primer would be an excellent way to stop your plaster from drying.
NOTE: The reason why water absorption is detrimental is that it will remove the water from your plaster mixture.
A good primer used for plaster is PVA, commonly known as wood glue, mixed in with water. PVA is an adhesive and allows the plaster to better stick to your wall. Other than that, PVA also reduces the porousness of a surface and gives you a smoother working space, making uniform applications much easier to achieve.
7. Wait for Rain
Rain tends to cause humidity, and this is a good thing if you want to keep the water in your plaster from drying up too quickly. Humidity is the concentration of water vapor in the area and tends to cause moisture. The condensation effect on your wall will increase its setting time.
8. Spray Water
Spraying a tiny amount of water onto your wall and to your newly laid-on plaster should do the trick if you need more time to spread it out. You should only spray in small increments as adding too much at once may end up thinning out your plaster.
9. Wetting Your Tools
Wetting your trowel in between applications will also help. Having wet tools entails that you’re also applying water, alongside plaster, onto your wall. You can get a bucket filled with water and dip your tools into it as needed.
To keep your plaster from drying too quickly, you need to slow down the process of evaporation. Evaporation happens when water molecules move too much due to heat and get pushed into the air.
Increasing the amount of water or decreasing its absorption/evaporation during application is key to increasing setting time.
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