Even though plastering jobs are diverse: repairing broken walls, restoring old homes, or adding a new wall, it is common knowledge that clean trowels are a must. Trowels covered in rust and old plaster affect the job by, first, adding foreign debris to the plaster mixture. This prevents the plaster from setting properly. The second is if you are aiming for that smooth eggshell finish. The coarse bumps on the trowel naturally adds texture to the damp plaster.
Among the important things to remember are the working conditions. The humidity and temperature factors and how you clean your trowels and other plastering tools in the UK climate.
A long soak and a good brush or sponge
It might seem too simple, but a good soak is enough to soften the plaster on stainless steel trowels. After a night or two, depending on how old the plaster is, take a sponge or brush and clean your trowel. You may also opt for warm soapy water if you are in a rush. Remember that when soaking your plastering trowels, to keep the handles above the water. If the handle is soaked this will affect your grip and may increase wood rot.
This method is advised for those who regularly clean their trowels. There is a consensus that the best way to maintain your trowels is to clean as you go.
Brick and sand
Another common method is to clean it like you would clean a knife. Add a little bit of sand and buff it against a brick, sandstone, or pumice. After the old flakes of plaster are gone give it a good rinse and it is good to go. The benefit of this method is that there is no prolonged exposure to water. The problem with soaking is if you forget you left it soaking in the first place. Besides the possibility of having the handle submerged, stagnant water can lead to rust.
The quickest way to get rid of old plaster and also the least advisable route is to use acid. Brick acid or muriatic acid takes the plaster off with no problem, but they are tricky to use. For brick acid, you have to get the proper kind of acid and be careful in handling it. For muriatic acid proceed with the same caution, but using muriatic acid is known to rust your plastering trowel faster.
There are other ways to clean your trowels like using WD40 or other similar products. There are also different ways trowels react to how you clean them. Cheaper trowels are known to be more temperamental during cleaning. When done wrong the trowel warps and becomes uneven. A brief soak, a brush, and drying afterwards is the best route in dealing with the trickier trowels.
Always keep your trowels clean. It is the best way to make full use of your investment in good plastering tools.