The Science Behind The Salt Painting Science Experiment: The salt absorbs or soaks up the water through a chemical action. After painting it and that damp patch coming and going, i did lots of research and found it was hygroscopic salts, the damp patch tastes salty too, i licked the wall hee hee Anyway, im sick of having the dehumidifier on all the time so sanded down the paint, right back to the plaster and sprayed some Salt Neutraliser on the chimney breast. Exposing the brick will mean once the damp issue is solved it will aid drying out so it will be fine to paint over but during drying salts will keep reappearing.

If the plaster was contaminated with hygroscopic salts then of course so is the masonry.

It doesn’t matter, just make sure you use one of the methods I referred to for the plastering: Renovating plaster Cement render Plasterboards on Laths or

1. So solving the damp in turn will solve the salt issue . Painting before the wood’s ready simply wastes a day’s effort.
Hygroscopic salts get lodged … Replastering old walls - indoors specification, the Professional Standard in the UK using Renderproof. A possible problem with applying paint to new plaster is that the plasterer has over trowelled or polished the plaster.

Painting Over New Plaster. Try holding a hair dryer against the damp patch and see if it dries out permanently.

I think it probably was caused by the dryer being close to the wall, keeping that area of wall constantly "damp", leaving you with the salt …


If it does, brush the fluffy salt deposits off, and paint the area of wall with a neutralizer.

Hack off all old plaster to at least 300mm clear of all signs of damp or salt and at least 1 metre above ground floor level - use a meter to test the walls and remove plaster at least 300mm above the highest level that readings can be obtained. The salts come from some form of moisture , either rising or penetrating damp . You cannot practicaly remove those salts so your meter will tend to over-read on the naked masonry. Most hygroscopic materials are salts, but many other materials display the property. Salt is hygroscopic which means that it can absorb both liquid water and water vapor in the air.

This is because chimney breasts are usually contaminated with moisture-attracting hygroscopic salts that have built up in the chimney structure as a result of the burning of coal over many decades. Water is an important solvent, so it's unsurprising that there is a term specifically related to water absorption.A hygroscopic substance is able to absorb or adsorb water from its surroundings. Consider the colour scheme prior to mist coating, as it will be preferable to mist coat in the same colour as the final coats to help build up to full opacity. Very common problem when the flue has historically vented gases from the burning of wood or bituminous coal. Typically, this occurs at or near ordinary room temperature. To paint pressure-treated wood successfully, therefore, you must be prepared to exercise a bit of patience. This Salt Painting Science Experiment is a fun way to combine art and science together. Efflorescence is a crystalline deposit of salts that can form when water is present in or on brick, concrete, stone, stucco or other building surfaces.It has a white or greyish tint and consists of salt deposits left behind when water evaporates.