We have always been determined to do the right thing and ensure that this stone-built, old house could breathe easy. The existing cement render was causing unnecessary damp issues by trapping moisture, prompting us to opt for a more breathable alternative – lime plaster.
However, after receiving quotes for work that were a long way outside of our budget, we realised that we would be taking on much of the plastering work ourselves.
One challenge we faced was the cost of buying ready-made lime putty, a key component of lime plaster. In response, we explored an alternative approach—mixing our own lime putty from quicklime.
NOTE: You can also explore pre-mixed plaster options, but we will come onto this another day!
Making your own putty is a little bit dangerous and a whole lot of fun! But let’s be honest, pretty intimidating for the first couple of times. It’s called slaking, the process of combining quicklime with water to produce a paste-like substance, lime putty.
We do this by putting a bucket full of quicklime into the tub and adding about double the amount of water to it and stirring with a long stick.
You should see the lime starting to bubble and ‘splob’ (technical term), as the reaction takes place.
We then mix again at intervals to ensure there are no dry lumps of powder.
Once the bubbling and steaming has stopped, I like to go in with a bucket trowel and scrape around the edge of the bucket, ensuring that no bits got missed. This sometimes sets the reaction off again, so do be careful!
TOP TIPS:
- Put the quicklime in the tub first, this avoids ‘pluming’ if you were to tip it in after. You don’t want to breath it in.
- If you haven’t added enough water, the bubbles will be very ‘splatty’ and more vigorous, which can make the whole process riskier. If it gets too dry, add more water.
- Avoid putting your head to close to the bucket, the steam is toxic!
- On that note, we use a long broom handle to stir the mix initially, that we can remain at a distance.
- ALWAYS wear appropriate PPE. Think long sleeves, a mask and goggles at the very least.
- Wait for the putty to cool before transferring it into another tub, it can still melt plastic after a few minutes!
Lime putty will last pretty much indefinitely in an air-tight tub, so there’s no rush to use it once you are done. Just check occasionally that there is still water on the top and if there isn’t, add a bit more to stop it drying out.
This traditional material has been used for centuries, before the more recent shift to non-breathable gypsum-based plaster. Beyond the practical aspects, the side bonus of lime plaster is that it offers a special finish to our renovation – it has a sort of softness that is beautiful.
While you can consider hydraulic lime powder as a substitute for putty, we found that it doesn’t provide the same level of elasticity in the mix, which makes the whole process so much easier to apply. This emphasises the importance of choosing materials that align with both the structural needs and those of the person doing the work.
Our commitment to lime plaster goes beyond a mere choice of material; it’s a holistic approach to preserving the heritage, functionality, and aesthetics of our home. By understanding the drawbacks of the existing cement render and exploring alternatives, we’re not only tackling damp issues but also ensuring that our renovation stands the test of time.
4 thoughts on “Lime Putty: Can you make your own?”
Thanks for the lime putty article. Been thinking about doing this myself. Will have a stab now. 🙂
Hi there, sorry I just saw your comment! Really glad it was helpful – good luck!
PS. Is this ok to use for repointing?
You would need to mix it with aggregates to the correct mix. We use NHL in our mix as it sets quicker, but putty will help make a stickier mix for pointing.