As soon as I got my hands on cement, this is the first project I tried to get the hang of it. I bought this geometric mold for my resin coaster DIY that I made a while back. Absolutely loved it. So, I made cement coasters too with that mold. Throughout the process I made some mistakes, figured them out and rectified in next ones. That is what I am sharing with you all this this DIY.
- Any oil
- Painter’s tape
- Geometric Coaster mold
- Geode shaped coaster mold
- Silicone bumpers
- Mixing container
- Mixing stick
- Water based clear Sealer – polyacrylic
- Sand paper or Sanding block
- Acrylic paints
DISCLOSURE: We only recommend products we would use ourselves and all opinions are our own. This post may contain some affiliate links. If you click through and make a purchase, we earn few pennies at no additional cost to you. It helps us to keep ‘The nomad studio’ alive. Thanks for support!
DOs and DONTs
- You can use any kind of mold for your casting. I have seen people use all kinds of material as mold. You can make silicone mold with this kit from amazon or buy one like I did in this DIY cement coaster or make one with melamine wood or use any plastic container. It really depends on the size of your object and what shape you want to cast. If you are casting a small and simple object, you can also make a mold in the desired shape with cardboard. Once concrete cures, cardboard can be peeled off easily.
- Prepping the mold: Make sure the mold is water tight. If you are using any material other than silicone or melamine, I recommend coating the mold with clean vegetable oil or some release agent. This will help a lot when you demold.
- Make sure that you follow the cement to water ratio as per the manufacturer’s specification. I have used ‘Cement All’ in this project. As per the direction, I used a 1:4 ratio. You want the mixture to be in pancake batter-like consistency.
- After you fill the mold, it is very important to release the air bubbles. So, give a few taps on all sides and corners of the mold. If you are casting a bigger item, pound on the mold with a rubber mallet.
- To add a personal touch, you can add liquid cement color to your concrete mix. In this project, I have only used acrylic paints to color the cement. In the case of acrylic paints, use as little as possible. Otherwise, it could affect the composition of the mixture.
- After curing, you should seal it with a water-based sealer. I use this polyacrylic sealer for most of my projects. It gives a little shiny finish to it.
DIY Coasters with cement
Step – 1: Mix the cement. Follow the ratio as per the instructions given in the package. I use the ratio 1:4 water to cement ratio for the product ‘cement all’. In this DIY, I have attempted to add some green and white acrylic paint to the cement mixture. But, remember to use acrylic paint as little as possible. Otherwise it might affect the cement mixture composition.
Step – 2: Pour the cement mixture of both colors in random proportion into the mold. I am using two types of mold in this DIY – Geometric Coaster mold & Geode shaped coaster mold. Next, tap on all sides. This will help to release the air pockets.
Step – 3: Let it cure for at least 24 hours.
Step – 4: Before de molding, try to loosen up the edges a bit. Since its a silicone mold, this process is very easy.
Step – 5 : Sand the whole piece and remove dust with clean towel.
Step – 6: Personalize it with any color paint you want. Finally finish with water based clear sealer. Adding sealer will also brighten up the color and gives a glossy finish.
Step – 7: Add bumpers or cork sheet underneath to protect the surface where you will keep this coaster.
If you take a closer look at the coaster in some places, there are air gaps . Those are formed if you do not release the air bubbles properly. I recommend that you give good amount of taps on all sides of the mold. I failed to do it in my first coaster that ended up having lots of craters. Its the top coaster in below image. Eventually, I got it right in next coasters. You can also see that in below image.