Amateur DIYers and home improvement newcomers fear few things as much as plastering. It’s a job with a reputation for being devilishly difficult to get right. Kezzabeth brilliantly sums up the frustrations which may arise in her blog post.
There’s one key thing any would-be plasterer can do, to boost their chances of success. That’s to ensure they mix their plaster correctly.
Our step-by-step guide on how to mix plaster will tell you everything you need to know, ensuring you always work with perfect plaster.
Tools & Materials
- Large bucket or mixing tub
- Drill with paddle mixer – You can also use a smooth, clean piece of wood if you don’t have a paddle mixer attachment for your drill
- Bucket trowel (to help clean your gear)
- Paintbrush (as above)
- Dustsheets or tarpaulin
- Clean water
- Finish plaster
How to Mix Plaster – Step-by-Step Instructions
A good way to think about mixing plaster is by comparing it to making a cake. To get the best result, you need to use the right ingredients, equipment and techniques…
1. Prepare for Plastering
Once you’ve mixed your plaster, you don’t have a lot of time to use it. It will set within 5 to 45 minutes, depending on the temperature and other conditions in your work area. You need to have everything ready to start plastering, as soon as your plaster’s mixed.
Before you start mixing, make sure the surfaces to be plastered are fully prepared. They must be clean and primed with PVA. You’ll also want to protect the wider room where you’re going to plaster with dustsheets or tarpaulin. This is a messy job!
Pro Tip: To keep mess to a minimum, consider mixing your plaster outdoors. Splashes and spillages are a fairly unavoidable part of this process, though remember you’ll have a heavy bucket of plaster to move back indoors once the mixing’s done.
2. Make Sure Your Kit is Clean
Before you get to mixing, ensure all the equipment you’re going to use is completely clean. That means your bucket or tub, your mixer and any other tools. This is critical; any dirt, stones or old plaster will mess up your new batch.
3. Add Water to Your Bucket
Set up the largest bucket or tub you can get your hands on. You want it to be much larger than the total plaster mix you’re going to whip up so that you don’t spill or splash too much. Only ever add clean water to the bucket.
The amount of water depends on how much plaster you need. A good rule of thumb is to work to a 1:1 ratio of water to plaster. You always add plaster to the water – never the other way round. If you tried to do this the wrong way, you’d end up with lumpy and useless plaster.
4. Gradually Add Your Plaster and Mix
Take around half the total plaster you’re going to use, and add it carefully to the water. Using your chosen mixing implement, start mixing the plaster into the water.
Mix carefully but thoroughly in both directions, getting right to the edges of your bucket and lifting your mixer up and down.
When your mix has reached a fairly smooth consistency with no noticeable lumps, add a little more plaster. Repeat the mixing process and continue until (a) you’ve used all your plaster or (b) the mix has reached an optimal thickness.
There’s no ‘perfect’ consistency. You need the plaster to be thick enough to bond to your surface, yet thin enough to be workable.
A good trick is to check that a small piece of wood can stand upright if you place it in the plaster mix. If you need any more advice on optimal techniques, check out this video on mixing plaster:
Pro Tip: You can also add what’s known as plaster retarder to your plaster mix during this step of the process. Plaster retarder slows down the process of plaster setting, giving you more time to work with it. DIY Doctor checked out one plaster retarder option, to see how useful it is.
5. Clean Your Gear
You don’t have long to use your newly mixed plaster. Before you get started though, clean your mixing equipment. If you don’t do this straight away, the residual plaster will set solid and become almost impossible to remove.
Any old plaster left on your bucket or tools will make them unusable for mixing future batches. The old plaster will contaminate any subsequent batches, ruining their consistency. A paintbrush wetted with warm water is usually effective at removing wet plaster.
6. Start Plastering
You’re now ready to start using your perfectly-mixed plaster. That might mean applying it to a smooth and simple surface or using it for a more complex repair job like the one The Carpenter’s Daughter found herself faced with. Either way, having perfectly mixed plaster makes your job much easier.
How to Mix Plaster – Final Thoughts
By following the steps in our simple guide on how to mix plaster, you’re well on the way to becoming a super skimmer. Having the right materials to work with really does make a tricky job so much simpler.