Multiple layers of paint applied over hundreds of years will often hide and disguise delicate architectural features. Paint can be removed gently, and without damage using a poultice and this sequence of photos shows how it is done.
We start with a sample section of historic plasterwork. Always test a small sample area first. I used Kling Strip. Always follow the Health and Safety guidelines provided – wear gloves and safety goggles.
The Kling Strip is applied to the plaster and smothered over using a trowel to about 5mm to 10mm thickness. It is then wrapped in clingfilm, to prevent it drying out.
The length of time required for the poultice to activate is dependent on the thickness of the paint layers and the substrate. In this case, it was left overnight but in more straightforward situations it might only need an hour or two. As the poultice activates you will start to see a brown-ish discolouration appear.
It is a combination of guesswork and experience as to how long to leave it before having a look. If several hours has elapsed it is worth just taking a quick look under the clingfilm to see if the poultice is dry. It should be kept moist and not allowed to dry out. If it is dry then just sprinkle it with some water to rehydrate. After a while you will feel you want to see if it is ready to take off, so just have a little pick at the edges to see if the paint has softened. When you are ready, the clingfilm can be removed and then you will need to carefully scrape off the poultice and in doing so you will remove the paint too. This requires some care and patience and also you will need so fine tools such as a scalpel, wire brush, water spray etc..
Once started, you keep going until you have removed the paint. It is easy to do, but be careful not to damage the plaster.
You can keep washing and brushing as you go. As it dries, the brown-isn colour will fade.
You will be left with the detail showing through once again, and the colour will continue to fade back to its natural state.
The time taken to remove the paint on this sample was about 15 minutes.