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Why has the paint near my new coating yellowed?

FAQ Details

Last Updated
13th o May, 2008

The Cause
This is a relatively uncommon, but recurring and often distressing problem for Floorsanders and clients alike. It occurs when a floor is coated with Polyurethane soon after the surrounding walls have been painted with certain brands of PVA white paint. What happens is that part or all of the walls turn pale yellow during the curing process of the Polyurethane. The effect is usually observed the day after coating has been applied. It has been demonstrated that paints made by Dulux, British Paints, Bergers and Taubmans do not generally exhibit this effect, and paints made by other manufacturers are not effected if they are given sufficient time to dry.

Generally, paint manufacturers do not disclose the ingredients of their paint, and therefore we can only postulate as to the cause of this phenomenon, the evidence suggests that there is a slowly evaporating ingredient in the effected paints, which reacts with one of the volatile components of the Polyurethane producing a yellow substance.

The remedy
It has been found that the offending yellow substance is readily oxidised by dilute chlorine solution rendering it colourless. Therefore, effected walls should be washed with a dilute ‘White king’ solution or similar. A better option is for the Floorsander to ask the client if the walls have been freshly painted with a suspected paint, and if so, then offer one of the following options;

  1. Plan ahead, and use a brand of paint known NOT to yellow,
  2. Plan ahead and have the floor coating completed and cured prior to painting the walls.
  3. Wait at leat one month for the paint to fully dry.
  4. Allow in the quotation provision for washing the walls with chlorine solution.
  5. Coat with an oil based coating; eg. MODIFIED OIL GLOSS, MODIFIED OIL SATIN or TUNGSEAL.
Visitor Comments
  1. Comment #1 (Posted by Max Boronovskis )
    Thanks for these FAQs. We have a new two pack lacquered (gloss white) bathroom vanity custom made for our bathroom which has come up with yellow splotching and yellowing after 30m2 of nearby floor was coated with Polyurethane. Any chance that is what happened here? From what I saw the two pack was rock hard when it arrived and there was about three weeks from its install to the urethane going down but I can't think what else it would be. I'll try to find what paint it was. I have asked the floor company for the msds of the polyurethane but they are yet to give it. My first assumption was that the floor sander shook some urethane off his hands while using the sink. When we were wiping the dust down the yellow splotches had dust clinging to them like there was actual droplets of liquid. When wiping first the dust came off then the yellow seemed to be wiping away but a faint stain remains. Can you recommend a dilution ratio for the white king or should I just start at 1:20 and test up? Max, Many thanks for your question. Initially Urethane Coatings recommend that you make every effort to obtain a Technical Data Sheet and MSDS for the finish applied to your floor and to the vanity. The Technical Data Sheet regarding the Vanity finish, should disclose what is compatible as a cleaner. Your comment regarding dust settling on the yellow splotches is clear confirmation that something has been spilled onto the vanity - My best guess is, it was the contractor applying the polyurethane onto the floor. This may have been Cleaning Solvent, Thinners or similar. Please apply extreme caution with use of White King as it is a bletch and is also abrasive (especially when concentrated) - its use may dull the sheen on the vanity. If you CANNOT obtain details of what is compatible with the vanity finish start with very dilute NON abrasive cleaners - and if unsuccessful move to moderately diluted Methylated Spirit.

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