Lime plaster has been used for building since before the use of cement. In recent years it has become more popular because it is more environmentally friendly than cement. Lime plaster can be made in two ways but it does require a fair amount of time and hard work to make it properly.
As you make your lime plaster, please pay careful attention to safety. When working with your lime plaster you should wear a mask, goggles, and gloves. Remember that you can generate heat when making lime plaster, so make sure not to work on top of any material that can be flammable, including newspaper or dry grass. This job may require two people. One person to focus on combining the ingredients while the other mixes. With both recipes, mix until all lumps are gone and run the mixture through a fine mesh screen to remove chunks of limestone. Store your lime plaster in a sealed container to protect it from the air for three months prior to using it.
Lime Putty Mix
Mix 1 part lime putty to 3 parts sand. The sand particles should range in size from very small, like dust,, to large pieces, as large as 3/8 inch, and they should be angular. Try to use only as much lime putty as you need to fill void spaces between the grains. The reason for the 1 to 3 ration in the mixture is that the empty spaces should take up about a third of the volume of most sands. Using smaller, grain-sized sand will result in a smoother lime plaster.
The longer the lime putty has to mature, the more solid it will become. It may be difficult to work with at first, but if you pound it on a large board with wooden mallets, the putty will become easier to work into the sand. This process can take a lot of work, but the beating of the lime putty is very important. As an alternative, you may find it easier to mix your sand with fresh, new lime putty, and then leave the entire mixture to mature for about three months.
Make A Hot Lime Mix
Combine 1 part quicklime powder to 3 parts sand. Add the quicklime to damp sand and mix them with a shovel. The mixture should be raked and mixed continuously, and may not require extra water, depending on the level of moisture in the sand. If you do need to add water, do so slowly, mixing as you proceed. Again, once your mixture is complete, you should allow it to mature for about 3 months.
Regardless of the recipe that you choose, when you are ready to use your lime plaster it should be beaten and worked until it has a nice, stiff consistency. It should be so sticky that you can hold it upside down on your trowel and it will not fall off. The more you work the mixture, the easier it will be to use. Add water sparingly, as extra water can result in cracking due to shrinkage when your lime plaster is finally used.