temperature & humidity

[Ric]

I think I may have stumbled on to something today, that I am sure the more seasoned of pen turner already knows. I have this theory that the ambient temperature of your work area plays an important part in the wood turning process, especially when using clear acrylic blanks(ie: circuit board pen blanks)
For the past several weeks now we(southern B.C. Canada) have been experiencing an abnormally cold winter. The night time temperatures have been going down to -25'C (7'F) Where as a cold night for us normally would be -3'C (28'F) with no snow just lots of rain (picture Seattle).
Thankfully my garage/shop is insulated & I have been running a parabolic heater when it turns deadly cold so my ambient temp is around 5'C (40'F)
I have noticed that when I am turning the types of blanks noted above, not only do I need to take extra care like I normally do when turning them, but I MUST be very aware of temperature fluctuation
My theory is:When you are performing any procedure where there is temperature build up, ie: sanding & polishing the blank in the final stages of turning, you are building up a tremendous amount of heat. When you stop this process the heat will quickly dissipate due to the ambient temperature in the room, especially if you have completely finished polishing the body & you are ready to take it off the lathe to measure & inspect it. Without thinking I immediately started to assemble the pen by pressing the parts together in my pen press.
Each time that I have completed this procedure in this manner I have cracked the body of both halves of the pen. Since Sunday, I have done this three times now, & did not believe it was so until on the third pen I was holding it in my hand when I felt & saw the pen crack.
Tomorrow I am going to set up another "batch" & try this again, as the cold temperature is not going away for another week or two I must press on (get it..Har..har.) however, this time I am going to take several more breaks in the finishing stage's so that the temperature does not have such extreme swings. Then, when I am satisfied with the finish, I am not going to take it off the lathe like I normally do. I am going to leave it sit on the lathe with the small amount of pressure exerted on it from the tail stock. Hopefully that should rectify the problem with what I conceive to be temperature fluctuation.
So folks, is there anyone out there that can agree with my findings or am I just completely out to lunch....Please advise, as I will welcome any thoughts & or suggestions you wish to submit..pro or con.


"IF LIFE HANDS YOU LEMONS...MAKE MOJITOS"
:knife: I noticed this knife in the "smilies" section, is that due to the increased popularity of knife making that Mr. Broadwell, & many others are spearheading, or is it for "the cut-ups" ?

 

[1080Wayne]

I think I would take them into the house to reach normal room temperature and assemble them there . Most plastics will be more brittle at low temps .

 

[jttheclockman]

Ric, why are you torchering yourself??? Yes we all know temp has alot to do with what we do. That is why we tell people to not leave their pens in the car in the heat or in the cold. You are dealing with such a small thinned piece of material weather it is wood or plastic. Wood is a natural material that will always move due to moisture. Metals expand and contract due to heat and cold. There is so many threads on this site explaining how to deal with tight fitting components and what to look for and what to do. Even doing a finish in a cold environment and then bringing into a heated area can induce problems. Not a good situation to be working in such extreme conditions such as that. Experiment all you want but you are wasting your time and materials. Temps do affect what we do.

 

[leehljp]

I agree and have written several posts over the years on this. Mine is very unscientific but from observations of posts from different people as well as my own experiences in different temps and humidity settings.

Hoadley has a book on "Understanding Wood" and it has a chart on the expansion rates of wood that first got me to realizing this. Mesquite does not expand and contract with temperature/humidity changes but pine, oak and most others do not. Also, the kind of cut has a direct effect on the movement.

The finish type is affected by the temp and humidity or lack of humidity. I have seen different responses from people in dry areas versus those in humidity areas.

I lived in coastal areas of Japan for 25 years Tokyo, Osaka and Nagoya with fairly high humidity rates but also dry times. I am from the mid-south (Mississippi) area near Memphis TN. We generally have high humidity 75% and more but have weeks of less than 50%. And our temp ranges from 100°F down to 10° to 15°F with humidity fluctuations. We have had upper 90s° with nearly 100% humidity and the 100s with 40% and less humidity. I had this in Japan and have it back here in the USA. The finishes of both CA and urethane are affected by the relationships of the humidity-temperatuation fluctuations. to what degree specifically and scientifically and which finish brands, I don't know, but there is an observable difference.

For me, I noticed the most changes in CA finishes drying when the temp dropped below 60°F. The hardening time increased. Dry times (a few weeks of less than 40%) made wood more brittle.

As to different finishes, the USA has an additive for lacquer called "Japan Dryer" that they don't have in Japan. It is an additive that was intended to make USA made lacquer dry in a format similar to Japan's famous urushi lacquer. (it doesn't.) But we can tell that additives and brands are affected differently by temps and humidity changes.

The wood movements and humidity level of the wood blank affect the finishes also. And it is naturally different from region to region unless the humidity and temps are the same. As mentioned in the beginning and often times by some old timers - using wood that has been dried 30 years or more are common. Snake wood, along with a few others are very temperature sensitive. Some people spent hours to days drill a snakewood blank, just to keep the temp down. Also Wood with high movement are more susceptible to cracking with temp and humidity swings.

Again, my observations are very generalized and from observations of different posts across the USA and world, as compared to where I have lived and experienced.

 

[Curly]

You might find it more effective to concentrate your pen making area so that the process occupies a smaller area that you can heat a little better. A tarp hung from floor to ceiling would work and you can take it down when it gets warm again.