Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

May, 2004

Polyurethane on Pine Floors

Q. We applied a second coat of polyurethane on our pine floors. Since then, temperature at night have been in the 40's and 50's while during the days it has been in the high 60's and low 70's. All doors and windows are open for ventilation, and on the 3rd night we turned on the heat in the basement to hopefully speed up the process. Yet, it has been 3 days and nights and the polyurethane has not fully cured. Does this mean that evaporation of the solvent was initially too slow and that it is trapped in the polyurethane? And if so, can this problem be corrected? Thanks for your time.

A. Polyurethane coatings are known for their solvent retention. In some cases, the polyurethane will dry from the top down. The surface will skim over quickly causing the remainder of the coating to stay soft and retain some solvent residue.

The first coat of poly on the pine floor would have penetrated into the wood so only a thin layer of poly would remain on the surface of the wood and dry and cure quickly.

The second coat now will not penetrate which means a heavy layer of poly remains on the surface. When it skims over it is dry to the touch but is not fully cured. The cause of the problem is solvent retention. Keep the room ventilated and warm and within the next few days it should be fully cured.

Best regards,

Tom Burke

Health and Safety

Please be aware that coatings and solvents are chemicals and therefore you should always pay attention to proper handling procedures and be prepared to wear protective clothing, such as respirators, gloves, coveralls, etc., and always be sure that your work area is well ventilated.

For further information on the health and safety requirements for the coatings and solvents you wish to use we strongly advised you to contact your local coating supplier and obtain a copy of the Material Safety Data Sheet (MSDS). If possible, go the extra step and look for this information on the website of the product vendor.

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