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Turning Green Bowl Blanks - okay to dry in an unheated northern shop?

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Forum topic by SawDustRUs posted 09-10-2017 05:22 PM 2005 views 0 times favorited 6 replies Add to Favorites Watch
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SawDustRUs

2 posts in 37 days


09-10-2017 05:22 PM

Topic tags/keywords: green turning drying bowl blanks moisture content unheated shop question pine cherry turning

Relatively new to woodturning. Currently rough turning recently cut cherry, white birch and white pine bowl blanks. Diameters range from 6 to 11 inches. I’m taking them down to about 80% of finished bowls and platters. Wall thicknesses are about 7/16”. Moisture content is averaging 20%. I’m weighing each bowl, placing them separately in paper bags, and filling the bags with species-specific shavings. I understand I’ll need to be patient for 6 – 9 months before I finish them off. I understand I should expect not all will “survive.”

I live in northern New England, where winter is a certainty. My shop is unheated (more technically, heated only when I’m using it). Is it “safe” to leave the partially turned blanks in my unheated shop during the freezing season?

Also – is there some standard for either a final desired moisture content and/or weight loss for each piece before tackling the final turning?

And, since I’m using the shavings, is it okay to skip the paste wax idea once rough turned?


6 replies so far

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Wildwood

2147 posts in 1912 days


#1 posted 09-10-2017 06:55 PM

Welcome to this message board.

If have a uniform 7/16” thickness may get some to dry but expect bowls going them to go oval. Uneven thickness and expect some to crack as they go oval. May find they dry faster than 6 to 9 months. Lot depends upon relative humidity in the shop or your area. Eventually will have to remove bowls from chips & bags to complete drying to EMC.

When you bowls stop losing or gaining moisture they have reach EMC whether that takes 2 or 3 month of more not for sure. Putting them back on your scale every other week and recording weight should get you in the ball park.

Don’t have air or heat in my shop, as long as changes in temperature changes not extreme don’t see a problem. Would recommend leaving bowl little thicker and allow for them to go oval. Lot depends upon diameter & style of bowl. My roughs normally a uniform 5/8”, 3/4” 1” and maybe tad larger.

Early on used to turn wet bowls completely to 3/16” or 1/4” and finish and wait for them to go oval had some cracked along the way but ended up with some pretty interesting result too.

-- Bill

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LeeMills

434 posts in 1079 days


#2 posted 09-10-2017 10:16 PM

Colder temps will probably slow drying somewhat. The “rule of thumb” for thickness of rough turned is normally 10% diameter so the wall of a 10” would be left about an inch.
I don’t use shavings but wax (anchorseal) exterior end grain and maybe an inch down the interior, then into a paper bag.
For me the EMC is 12-14% so I consider <14% good to go for final turning. I do try to bring mine in the house for the last couple of week to let the wood acclimate to the lower moisture in the house.
On about page six starts listings for EMC for most major cities.
https://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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Wildwood

2147 posts in 1912 days


#3 posted 09-11-2017 06:37 PM

Table 2 EMC chart on page 6 is nice to know information but doesn’t take into account average annual relative humidity. Look at date of that information. A better guide is found in chapter 13 on page 5, Figure 13-1 and Table 13-2 this will give you ballpark numbers to shoot for.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_13.pdf

Yes cold weather will slow down or stop wood drying process altogether. If stop and think about it drying wood is simply a water removal process accomplished by evaporation. Simple air circulation is all that is required.
Yes still want to slow down the process to keep wood from checking and cracking. Depending upon where you live just a paper or plastic bag is sufficient for breif period. High relative humidity use paper or cardboard box low relative humidity use plastic. Chips okay too but be careful not to leave more than week or two depending upon time of year and where you live don’t want to encourage mold growth.

When harvesting wood something have to keep in mind is preventing fugus or mold growth. How you handle, & store wood could lead to this stuff growing. One reason only use plastic bags to wrap a bowl or spindle blank while mounted on the lathe is taking a break (going to lunch or overnight) because where I live. So times of the year are real bad and other time not a big concern.

See page 2 Figure 14-1 Climate index for decay hazard.
https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_14.pdf

When harvesting wood for turning lot depends upon moisture content of of that wood. Freshly cut or tree been down for awhile matters.

-- Bill

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Wildwood

2147 posts in 1912 days


#4 posted 09-11-2017 06:45 PM

Depending upon how wet the wood is rough turning will dictate use of paper bags, boxws or chips, or just turning to uniform thickness and store on the floor in corner of my shop until ready to finish turn.

Some people claim coating the end grain using wax emulsions prevents all kinds of woes. Are you tuirning an end grain or side grain bowl? While believe end grain bowls or hollow forms might benefit from coating side grain not so much. JMHO!

-- Bill

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SawDustRUs

2 posts in 37 days


#5 posted 09-15-2017 06:51 PM

Just joined and this was my first posted question. I’m overwhelmed by the information you’ve provided. Thank you very much. I feel I’m on more solid ground as I continue the work (joy!).

Mike

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Wildwood

2147 posts in 1912 days


#6 posted 09-16-2017 10:37 AM

Very old article on turning wet wod thin. I don’t like mentioning “PEG,” but he explains learning curve is pretty steep and expensive.

http://customwooddesign.com/turninggreenwood-1.html

John take turning wet wood a little further in his article.

http://www.johnjordanwoodturning.com/John_Jordan_Woodturning/Understanding_Wood.html

Everyone has to come up with their own plan turning green or wet wood based upon where they live and yes there will be some surprises along the way.

-- Bill

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