Applying finish in closed shop

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Forum topic by jwinburn posted 07-02-2020 02:32 AM 548 views 2 times favorited 7 replies Add to Favorites Watch
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9 posts in 2563 days

07-02-2020 02:32 AM

Topic tags/keywords: safety finish ac respirator

I live in Tennessee and the humidity here makes dry times difficult at times and just plain uncomfortable. Does anyone have any suggestions on safely applying finished in a closed garage so my ac can keep the temps and humidity reasonable?

7 replies so far

View Walker's profile


465 posts in 1693 days

#1 posted 07-02-2020 04:33 AM

Open the garage door? : )

I do everything in my basement shop including finishing. There are two very small windows (4”x12”) but it’s not ideal at all. I run a few fans to try to get some degree of air exchange. Experiment with various products and find what works best in your situation. So far I’ve found Tried and True brand products and milk paint both dry quickly and are low VOC, which helps in a non-ideal environment. If you really can’t open the garage door my advice is to 1) Lower expectations. 2) use low VOC products 3) add a lot of extra dry time 4) finish at the recommended temperature if possible. 5) Lower expectations.

This is what Waterlox says on their website:


Proper ventilation and adequate air circulation must be provided when using any wood finishing materials. Most oil-based varnishes dry upon exposure to oxygen, which is also known as “oxidative cure.” A lack of cross-ventilation (air exchange) provides less free oxygen, slowing the drying process. Cross-ventilation is the biggest factor affecting dry times. It is not recommended that any solvents or solvent-based materials be used in a non-ventilated area. It is the oxygen molecules in the air that interact with the varnish, creating a chemical reaction and causing the film to dry. Therefore, the better the ventilation (during and after all coats) the quicker the film obtains its final hardness and other chemical resistance properties.

ASHRAE (The American Society of Heating, Refrigerating and Air Conditioning Engineers) states that the typical air exchange in a residence using only mechanical HVAC can be as low as 0.35 air exchanges/hour. In most cases 0.35 air exchanges/hour will not be adequate to dry Waterlox in 24 hours. We therefore strongly suggest achieving a gentle flow of air by cross-ventilation. This can be achieved by the use of a box fan running at low-speed in a window or door exhausting to the outside air as well as an open window in some other part of the room or house to achieve 3 – 4 air exchanges/hour. Not only will this aide the drying process by pulling in fresh air loaded with oxygen, but it will exhaust the solvent odor.

Read the directions on the label completely before using, including information related to the use of a respirator while applying the finish. Lingering odor indicates inadequate ventilation, high humidity or both. If you cannot ventilate the area choose another product.

Be sure to use proper ventilation:

While applying the coating,
During the curing process (first 24 hours after each coating is applied), and
Continue to ventilate the area for 7 days after the final coat is applied.

Examples of poor ventilation:

Ceiling fans do not bring in fresh air from an outside source, even if windows are opened. They circulate stale air around the room. In fact, ceiling fans have a tendency to direct too much air downward on the surface of the freshly applied coating and can potentially “skin” over the fresh coat. This slows down the drying time because the solvent is trapped beneath the skin, causing a longer or improper cure.
Heating and air conditioning do not provide enough ventilation. Opened windows with air being exchanged, replenishes the room with fresh oxygen and vents the evaporating solvents.
Closed doors cut off airflow in a room even if a window fan is in place. If the window fan is working properly, solvent odors should be exhausted and will not enter connected rooms.
Closets are typically the most difficult areas to ventilate – leave closet doors fully open.


Always read the Waterlox label instructions closely before using, including information related to the use of a respirator while applying the finish.

Edit: after re-reading the waterlox advice, I’d guess that water-based finishes would work better then solvent based for a closed room.

-- ~Walker

View CWWoodworking's profile


2129 posts in 1399 days

#2 posted 07-02-2020 01:10 PM

Which finish?

View CaptainKlutz's profile


4870 posts in 2715 days

#3 posted 07-02-2020 01:39 PM

+1 Tried and True Finishes
The Original Wood Finish, Danish Oil, and Varnish Oil do not contain solvents and have pleasant sweet odor for couple days till cured.

Every other wood finish I have used, iespecially commercial water based products requires adequate ventilation.

Some will claim that water base products are ‘safe’ in enclosed space; but if you read the mfg warnings; they all release glycol and alcohol that are dangerous in high concentrations. The catalyzed versions using hardener additive tend to release more dangerous chemicals that require ventilation or you will get sick.

Lowest odor, least dangeous, water based coatings are indoor latex paints. Often can buy a clear version of them labeled as tint base #4 or #5. They will look cloudy in can, but are clear after drying. Most big box store paint employees have no clue about clear latex availability, so don’t bother asking for it.


-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View cracknpop's profile


520 posts in 3569 days

#4 posted 07-03-2020 12:00 AM

Knowing what finish you are using may allow better recommendations.

I’m north of you in Indiana and share your hot and humid summers. When spraying lacquer, I turn on my shop made air cleaner which will catch SOME of the overspray but is not adequate by itself. I will also put a window fan turned on low blowing into the shop in one window and crack open another. I will turn the fan on as soon as I am done spraying a coat and leave it running for a few minutes. All the while continuously wearing a respirator.
Yes, I begin to loose some cool air and temps will begin to rise. But by the time I’m done spraying I’m ready to call it a day and AC can catch up by the time I get back into the shop. Make sure to frequently clean your AC filter!
I do the same when spraying shellac.

-- Rick - I know I am not perfect, but I will keep pressing on toward the goal of becoming all I am called to be.

View OSU55's profile


2821 posts in 3210 days

#5 posted 07-03-2020 12:37 PM

I live in SW Missouri & share hot humid summers. I use a window ac unit. This time of year solvent based finishing is done early morning or after the sun goes down. I spray mostly lacquer and some shellac. I use a filtered 1000 Cfm blower, open the man door in back and open the garage door. I shut off the ac. I use retarder to prevent blushing. Always use an organic vapor respirator. 10 min after spraying I can close things up, the solvents have flashed. I usually spray 2-3 coats tho and just leave things open.

Also do a lot of wipe on poly. I keep things closed up till Im done, then open things up to clear the vapors. I do wb finishes this way as well.

View JackDuren's profile


1689 posts in 2180 days

#6 posted 07-03-2020 01:01 PM

I spray in the garage. I turn the heat off, open the door spray , let fumes out and close door. Summer time the same except the air stays on as its on central….

View jwinburn's profile


9 posts in 2563 days

#7 posted 07-03-2020 01:25 PM

Thanks so much for your suggestions. I usually use shellac, wipe on poly, and oil based stains usually. I’m opening up to more water based finishes. I just have it in my head they’re not as durable buy I understand that’s probably not the case. Again thanks for the great ideas. Stay cool

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