Preservation Of Stones
For preventing the deterioration and decay of stones preservation is a very necessary and important practice. There are different processes for prevention which varies from stone to stone.
Here are some of the most used ways of preservation of stones:
1. Protective Coating
Usually, a protective coating over the surface of the stone is made to prevent it from deterioration, and it's done by these three steps:-
- Firstly, Stones are dried with a blowlamp.
- Then, Paraffin, light paint, linseed oil, etc. is applied over it to make a protective coating.
- In case of linseed oil, it is boiled and applied in three coats over the stone and then the coating of dilute ammonia in warm water is made.
*This process is a temporary process and it is necessary to do it periodically.
2. Washing Stones
- Preservatives are applied on stone and then it is washed with potash or thin solution of silicate of soda.
- CaCl2 Solution is applied after drying the stones.
- The solutions combine to form the lime silicate which prevents stones from decay by filling the pores of it.
- The salts formed in the process are washed out later.
*The Solution of silicate of soda and solution of CaCl2 is called the Szerelmy's Liquid.
3. Prevention By Barium Hydrate
Solution of Baryta, Ba(OH)2 or Barium Hydrate is used for the prevention of stones from sulphate attack.
- Since the Calcium Sulphate present in stones on reacting with soot and dust of atmosphere forms a hard skin makes stones attack prone.
- So, Ba(OH)2 or Barium Hydrate or Barium Hydroxide reacts with Calcium Sulphate, CaSO4 to form insoluble Barium Sulphate, BaSO4 and Calcium Hydroxide, Ca(OH)2.
- So that, Ca(OH)2 absorbs CO2 from the air and from Calcium Carbonate, CaCO3 for prevention from deterioration and Sulphate attack.
4. Painting Stones
Painting with coal tar and lead paint is also used for preserving stones but it has some demerits or disadvantages as follows:
- Spoils the colour of stone.
- Spoils the beauty of stone.
- Introduces salts in the composition of stones which leads to further damage of stones.
*Overall, it is not a good practice for preservation of stones.
For the factors due to which stone deteriorates, check- https://www.akhandduttaengineering.in/2020/07/deterioration-of-stones-stone-as.html
*Source- Internet, Books and Self-Analysis