Winter and woodworking.

[James Brothers]

I am nearing the completion of a project I started earlier this year but I’m having a little trouble. The problem is my shop, there is no possible way for me to heat it. I live in an apartment complex and my shop is set up in my garage. I was lucky enough to have the building manager ok the shop, but he absolutely will not let me add heat.
I don’t mind working in the cold I’m just not sure what effect it will have on my project. I guess my question is, is it possible to finish in the cold? What effect will it have on the wood and the finish? If you have any ideas our input I would like to hear it thanks.

[glenn bradley]

Depends what you call cold. Where I live cold is anything below 55 to 60 degrees. We do get into the low 40's during our brief winter and I observe the range stated on the finish of choice. After hours of work on a piece I am more than willing to wait on the weather to finish it up without issue. Humidity can be an issue some places as well. If your pics are current for this time of year I would say that looks like a good day to finish right there in the pic.

I would not try to squeeze a finish job in if you know the temp is going to drop over the next hour or so (as in just before sundown). I keep an indoor/outdoor thermometer in the shop to tell me for sure when it is a good idea to open or close the door vs. what I think I feel in the air.

[Doug Shepard]

No heat in my garage either. I currently have a workbench top on sawhorses in the living room for temps high enough for epoxy to cure. I'll have to do the finish in there as well once I get to that point. Spray finishing is pretty much out, but I've finished a number of things inside with no problems. Wipe on poly, tung oil, and even shellac smells dissapate pretty quickly. The kitchen table works well for small stuff as it's near the exhaust fan over the stove to pull the smell out even quicker.

[Rick Gifford]

You need to finish this in a warm area. You dont want to ruin all your hard work now.

I will assume your manager is concerned about fire with this being a garage building. Maybe he would consider allowing you to operate a propane spaceheater in the center with you present. Tell him it wont operate while unattended and you would appreciate getting the finishing done on this. It would be worth staying with it while the coats dried.

If he absolutely will not agree, possibly find a friends place to do the finishing.

Or clear a room (dining or kitchen) and take it up into your apartment. I'd even consider laying down a tarp and finsihing it right in the living room.

[Steven Wilson]

Well how cold is cold? I'm able to get a decent shellac finish down to freezing, otherwise you need to be around 70F. Another option is to bring your piece into the apartment, lay down drop clothes and finish it there.

[David Epperson]

I'm in somewhat of a similar predicament. Any all woodworking will have to be done in unheated space, some outdoors in an open "carport". Finishing I can probably do in a closed in back room that could be heated to the temps required for the finish. But I'm more worried about wood movement from a sudden temp/humidity change. I'd hate to "suffer" through making all the cuts in the cold only to try and finish a piece that is busy trying to self destruct warping and twisting. Is this a big issue?

[Jim Becker]

You can get a space like that up to a comfortable temperature in a reasonable amount of time using an electric heater or two. That's how I work in my shop during the winter months. As stated, finishes don't like extreme cold. Shellac will "work" at lower temps since it's an evaporative finish...the alcohol will still flash off in the colder temps, although a little slower. But for best results, get things up to temp.

Alternatively, build your winter projects with the intention of completing the finish in the spring. Smaller, decorative projects can also be finished with BLO and wax...and that you can do on your kitchen table. There is a small mount of odor, but it's not noxious.

[David Epperson]

You can get a space like that up to a comfortable temperature in a reasonable amount of time using an electric heater or two.

Thanks Jim. But again I'm just a bit more worried about all that wood that gets planed, rendered flat, joints cut, assembled, brought inside, and in the middle of warming up to finish decides to go corkscrew on me. This pear wood has a reputation of doing that, and I'v lost one piece to some severe twisting. So much so that In the summer I tend to apply a 75/25 mix of Mineral Spirits/BLO to the wood right after planing or any serious exposure of new surface to slow down the moisture change. Since this is not an option on the colder days as the BLO won't really cure that cold. Is this overkill?

[Steve Schoene]

If you want something to slow moisture transfer, shellac is better than just about anything, and it will dry in much colder temps than most of the others, as was stated. And, it dries so quickly that you wouldn't have to heat the space for very long to give it a pretty normal drying time. Thinned BLO won't have much effect anyway.

[michael osadchuk]

"But I'm more worried about wood movement from a sudden temp/humidity change. I'd hate to "suffer" through making all the cuts in the cold only to try and finish a piece that is busy trying to self destruct warping and twisting. Is this a big issue?

"

....my understanding is that temperature change has very little impact on wood movement; it is changes in relative humidity of the atmosphere that causes wood movement......
.......and unless your indoor house environment is tightly stablized by airconditioning/humidifiers/dehumifiers, the relative humidity between indoors and outdoors is not radically different on any specific day.......

[David Epperson]

"

....my understanding is that temperature change has very little impact on wood movement; it is changes in relative humidity of the atmosphere that causes wood movement......
.......and unless your indoor house environment is tightly stablized by airconditioning/humidifiers/dehumifiers, the relative humidity between indoors and outdoors is not radically different on any specific day.......

Well one of us needs to revisit our research. I was thinking that it was absolute humidity, %water vapor, that did not change much from indoors to outdoors - relative humidity will change drastically with temperature under those conditions. The warmer the air gets, the more water vapor it possibly can hold, so it lowers the relative humidity. The dew point is that temperature where the current amount of water vapor in the air becomes 100% relative humidity. So moving lumber from a cold outside area of high relative humidity, but low absolute humidity in the winter, into a much warmer area with the same absolute humidity would result in a much lower relative humidity. Which would cause the wood to move a bit more rapidly.

Of course if I'm wrong about this I don't have much to worry about. I just don't think I'm wrong.

But if you were talking about changes in the temp of the wood instead. you're probably right. I do not know.

[Howard Acheson]

Here are the basic temperature/humidity considerations for most finishes.

Oil based: The drying time on the label is based on 70-75 degrees and 50% relative humidity. This pretty standard for all finishes. For temperatures of 60 degrees, the drying and curing time will be about double. For 50 degrees the finish may get "dry to the touch" but the curing will be very slow and may not occur at all even if later brought into a warmer environment. Temperatures above 90 degrees with high humidity will also significantly slow drying times. The item being coated, the finish and the air temperature must all be kept above 60 degrees for all of the curing time.

Note: Oil based finishes "dry" in two steps. First, the thinners evaporate and the item becomes tack free. However, the most important process is the reactive curing where the oxygen and finish react to form a hard, durable and well adhered film. The curing process takes from 3-4 weeks.

Shellac and Lacquer: These finishes are evaporative finishes and as long as they can evaporate, the finish will "dry and harden". That said, I would not apply either below 35-40 degrees. Basically, there is no curing process with either and as soon as it is dry, the item can be handled. However, I like to wait 48 hours after the finish coat before using or "finishing the finish".

Waterborne: Waterborne acrylic finishes are a two step drying finish. The first is the evaporation of the water and the second is the coalescing of the other chemicals into a film. This second step requires that the temperature be about the same as oil based finishes. Below 50 degrees the coalescing process may fail completely. At 60 degrees it is significantly slowed. More than other finishes, waterborne finishes are affected by relative humidity. In high humidity, the water evaporation is slowed. Above 90% it is real slow. At under 25%RH, the evaporation may be so fast that the finish does not flow out properly.

So, there is a range where finishes work best and there are low and high points where a finish may not dry or cure at all. As you approach those points, the finish may begin to behave badly. It may not flow out and visible brushstrokes are much more apparent. It may drip and sag more easily and bubbles may also be a result.

[michael osadchuk]

Well one of us needs to revisit our research. . So moving lumber from a cold outside area of high relative humidity, but low absolute humidity in the winter, into a much warmer area with the same absolute humidity would result in a much lower relative humidity. Which would cause the wood to move a bit more rapidly.
But if you were talking about changes in the temp of the wood instead. you're probably right. I do not know.

David.....You are absolutely right: your post drove me to back to read Bruce Hoadley "Understanding Wood" (first edition)...... and he clearly agrees with you regarding relative humidity typically being significantly lower indoors than outdoors in winter (and the reverse in summer) and because it is changes in relative humidity that directly affects equalibrium moisture content of wood which in turn cause wood movement......
.... for a real life example today I took outdoor temperature and relative humidity readings where I live (north of Toronto, Canada; snow melting after an early season snowfall): the temperature was 2 degrees Centigrade/34 degrees Fahrenheit and a relative humidity of 56%; I brought the weather gauge indoors (electric heating; no humidifiers) and the temperature was 22 degrees Centigrade/70 degrees Fahrenheit with the relative humidity reading being 33% - a drop of 23%...as you state, bringing wood from outside to indoors in such an instance would lead to a bit more wood movement (contraction).......

Hoadley also said temperature change ALONE has virtually no thermal expansion/contraction effect on wood;it is the change in relative humidity typically associated with indoor/outdoor and seasonal weather changes that has the big impact on wood.....


thanks for correction; reading Hoadley, though interesting, hurts my head (swollen head now shrinking...smiley)

Incidentally, I keep track of seasonal relative humidity changes in my basement workshop which is well insulated, has a bit of electric heat and no humidifier/dehumifier: the temperature typically stays above 60 degrees Fahrenheit and doesn't exceed 75 degrees, while the relative humidity can swing from a low of 20% on some days in late January and February to a high 65-70% on some rainy days in late summer; despite this wide swing in relative humidity, moisture readings on unfinished, kiln-dried wood stay between 6 and 10% year round

[David Epperson]

David.....You are absolutely right: your post drove me to back to read Bruce Hoadley "Understanding Wood" (first edition)...... and he clearly agrees with you regarding relative humidity typically being significantly lower indoors than outdoors in winter (and the reverse in summer) and because it is changes in relative humidity that directly affects equalibrium moisture content of wood which in turn cause wood movement......
.... for a real life example today I took outdoor temperature and relative humidity readings where I live (north of Toronto, Canada; snow melting after an early season snowfall): the temperature was 2 degrees Centigrade/34 degrees Fahrenheit and a relative humidity of 56%; I brought the weather gauge indoors (electric heating; no humidifiers) and the temperature was 22 degrees Centigrade/70 degrees Fahrenheit with the relative humidity reading being 33% - a drop of 23%...as you state, bringing wood from outside to indoors in such an instance would lead to a bit more wood movement (contraction).......

Hoadley also said temperature change ALONE has virtually no thermal expansion/contraction effect on wood;it is the change in relative humidity typically associated with indoor/outdoor and seasonal weather changes that has the big impact on wood.....


thanks for correction; reading Hoadley, though interesting, hurts my head (swollen head now shrinking...smiley)

Incidentally, I keep track of seasonal relative humidity changes in my basement workshop which is well insulated, has a bit of electric heat and no humidifier/dehumifier: the temperature typically stays above 60 degrees Fahrenheit and doesn't exceed 75 degrees, while the relative humidity can swing from a low of 20% on some days in late January and February to a high 65-70% on some rainy days in late summer; despite this wide swing in relative humidity, moisture readings on unfinished, kiln-dried wood stay between 6 and 10% year round

Well dang. This is one of those cases where it really would have been nice to have been wrong as it puts me in a bit of a catch 22 situation. The pear wood I would like to be working with has a reputation for twisting when it warps. It's been stickered and air drying for just over 2 years and I was going to try and get some projects built out of it. I'm confident that once sealed with some sort of finish it will remain stable. But to do this I may have to bring the indoor heated space to the same RH as the colder outside by pumping quite a bit of moisture into the heated spaced. Not sure if I know how to do that in a controlled manner just yet.
Of course the intent was to get these things made before it turned cold -but life had different plans.
I would like to thank you though, as it was your examples of measuring the conditions that showed me how I just might be able to get around my issue. I think I might be able to keep a matched RH.

[michael osadchuk]

The pear wood I would like to be working with has a reputation for twisting when it warps. It's been stickered and air drying for just over 2 years and I was going to try and get some projects built out of it.

I wonder if you have another issue to deal with: if all the air drying of the pear wood has been outside and the destination for the finished piece is indoors, before you work the wood you MAY want to further reduce the equalibrium moisture content the EMC that wood items to inside the home will eventually aclimatize to.
The "USDA Wood Handbook" (downloadable free; enter the title in an internet search engine) gives the EMC for outdoor use of wood in Little Rock, Arkansas as averaging around 13.5% while the recommended EMC for interior use of wood in your area as between 8 and 11%.
If you decide to reduce the EMC to the recommended for interior use number, one way to do it would be to bring the wood inside, sticker it, preferably in a warmer/LOWER humidity part of the house, even though you will cut/assemble the piece outside.

Another interesting website to check regarding wood movement, etc. is www.woodweb.com, the wood industry's primo website; their 'knowledge base'/forums are well-organized and moderated by experts to correct misinformation.

.....I suspect that this book knowledge may not be as meaningful as consulting with a woodworker in your area who has experience in doing what you want to do ....

good luck