Cold Temperatures Retard Floor Finish

A cautionary tale: with the room at 50°F, a poly floor finish fails to cure. October 18, 2012

I need experienced advice on some wood floors I am in the process of refinishing. Minwax high build poly was applied approximately 15 hours ago. Applied as thin as possible to still get coverage. The average temp has been about 50 degrees, humidity about average for the NE US. Have all windows open and a fan drawing air. This stuff is still tacky/gummy. Your fingernail can pull it up, makes dents, etc. I am not experienced with poly, as I spray finish. I am thinking it is just taking a long time to dry for whatever reason, but 15 hours and still not even solid is unusual, isn't it? I called SW techs and they told me I must have put it on too thick and I should wipe down with MS to reactivate the top layer. We deliberately put it on as thin as possible to make the gallons stretch. Furthermore, how am I supposed to walk on it to get to areas for solvent wipe?

Should I panic? If it is just an extremely slow drying product, can I add anything to the next coat to speed up the process, like japan drier or something? The tenant is planning on moving in soon. I thought 4 days would be more than enough to put two coats on this floor.

Forum Responses
(Finishing Forum)
From contributor C:
You need to warm up the room. It is way too cold. Try with a hair drier on a small section to see if it will cure.

From the original questioner:
Thanks. 50 degrees being too cold didn't even occur to me. I am so used to lacquer and CV, which are ever so forgiving. I did notice that as the temp climbed to about 55 today the stuff started to dry better. The previous tenant was nice enough to leave the oil tank bone dry, so I can't turn the heat on. If it still isn't dry tomorrow, I will have no choice but to get some oil. Interestingly, the brush marks on the can and such are also still a bit soft. The can was indoors at 70 degrees for the whole time period (19 hours at this point). I think the Minwax high build poly is just very slow drying. At least it is drying and I don't have a sticky disaster on my hands. I thought about going to a flooring place and getting a pro level product, but SW was local and had 30% off. Guess I got what I paid for.

From contributor L:
You didn't say what it was applied on. Was it a freshly sanded floor? Or did you just apply it to a floor that was just swept? Not drying is usually a sign of applying a finish over wax. It could be the cold, but even at 50F it would be dry in a few days. Poly usually dries in 4-8 hours at 70F.

From the original questioner:
It was applied to a freshly sanded floor. I think I just got a hold of a slow drying product. It has been over 24 hours now and you can still pick it into little gummy balls with your fingernail. I am not the one who applied it, but was there when it was being done and it was not put on overly thick. I did tell the person applying it to put it on as thin as possible, but maybe I was speaking German.

If the stuff is temp sensitive, then it should say that on the can. I'll wait until the last minute and hope it is dry enough to sand. The poly I have used in the past is rock hard within about 24 hours, so that is why I am worried.

From contributor L:
The website says this:

"Note: Dry times are based on good ventilation, temperature of 77°F and 50% relative humidity. Lower temperature, higher humidity, lack of ventilation or application of thick coats will extend dry time. Slight ambering may be experienced when polyurethane is applied over light-colored wood surfaces. Always spot test on an inconspicuous area to ensure satisfactory results. For light-colored wood surfaces, we recommend protecting with Minwax® Polycrylic® Protective Finish."

From contributor R:
Remove it. I've had various finishes act weird and it never works out the way it should. I've pressed on and come up with some plan to make it work, but over the years I've found that taking it back to the beginning and removing the offending material is always best. It also makes you concentrate a little better the next time you start your schedule. There are hundreds of reasons that hundreds of different materials don't work correctly and there are many hundreds of workarounds for the problem. The best one is, Start Over.

From the original questioner:
So it has been 50 hours now and the stuff is almost hard in most places. Spots where it was put on a little thick can still be gouged with a fingernail. Spoke with Minwax and they assured me it would probably dry eventually. I guess I will have to move furniture, etc. to put on the second coat down the road. The weather is not cooperating, as highs are going to be in the 50s and lows in the 30s for the next few days. Guess I'll chalk this one up to experience. Thanks.

From contributor B:
Go to a rental yard and get some kind of heater in there. Or get the oil for the home heater. It'll make your job a whole lot easier.

From contributor K:
Crank up the heat, but do it safely. Beware of vapor buildup!

From contributor B:
Also, when you do the second coat, heat up your finish (put the cans in buckets of hot water) before you apply it.

From the original questioner:
Thanks. I dumped in some diesel and fired up the heat. Also dug up some electric space heaters. That helped a lot. It has been over three 24 hour periods now and the stuff is almost there. I'm a little pissed Minwax didn't put a solid warning on the can about temp sensitivity and film thickness sensitivity. Especially considering this product is geared to homeowners. Very irresponsible. If this had happened on a customer's project, I would have my pants down right now.

From contributor L:
Pretty much standard practice that when you are finishing - you need to have warm temps. 65+ is standard and 70-75F is good practice. Anything below 50 is not going to work well. Just about any finish goes by these rules.