cat faces on newly painted wall - chemical reaction

B

BLOB

Registered User
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hi all,
I have a friend with a problem. They have just put undercoat on internal walls of house and marks which I think painters call ''cat faces'' keep coming out.......... it appears to be a chemical reaction between hardwall and paint.....

the builder has suggested using an oil based undercoat - however, the painter sayes this would be too time consuming and expensive.........

Has anyone ever had this problem and if so..... whats the solution.

cheers
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BLOB said:
hi all,
I have a friend with a problem. They have just put undercoat on internal walls of house and marks which I think painters call ''cat faces'' keep coming out.......... it appears to be a chemical reaction between hardwall and paint.....

the builder has suggested using an oil based undercoat - however, the painter sayes this would be too time consuming and expensive.........

Has anyone ever had this problem and if so..... whats the solution.

cheers
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Click to expand...

Just use oil based paint on the areas where the cat crap is.
 
could you diluted polybond first to prevent the reaction its cheap and takes no time to apply ask the builder if it will work
 
thanks alot, I have passed on your comments to by friend. I had also emailed the paint company who sent an email and also rang them giving lots of advice........


''This problem ( known as Mapping or Murphys Defect ) is due to variable porosity of the plaster surface, generally caused by overtrowelling of the plaster. The areas where the paint is slow to dry have low porosity and often the surrounding areas where the paint is absorbed readily show a build up giving the "map" appearance.
This mapping problem only occurs on solid block plastered walls and not on plasterboard surfaces such as ceilings or partition walls.

The problem cannot be seen in the raw plaster state, it only becomes evident when paint is applied.

Generally, when the first or second coat of emulsion has fully dried application of additional coats are OK. It may be necessary to sand any raised areas to even up the surface. As a last resort you can apply a coat of Dulux Sealapore which seals the surface and evens out the porosity.''

thanks again
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