drying wrapped in paper

[Scott Brandstetter]

I am in the process of drying my first few bowls in paper and have a few questions.

1. I bought kraft paper on a roll from Home Depot. Any issue with that. It's about the weight of a paper grocery bag
2. I have them sitting in my basement shop. Temperature in the shop approx 66 degrees. I could also put them in a solid concrete room (floor, walls and ceiling). Would that be better because its a bit cooler and a little higher humidity?
3. I don't have a fan blowing? Is air movement more that the normal air in a house okay or having a fan better?
4. Kind of surprised but bowls started out at 35% and after 10 days only down to 25%. Not sure why I'm surprised since Ive never done this before but thought they would dry quicker. I have them down to approx 3/8 thick with the plan of finished thickness of 1/4 inch after final shape and sand.

Any help would be appreciated

 

[hockenbery]

Scott

This is what I'd do.

I use two paper bags.
Put the bowl in one and slide the other bag over the opening.
I put them in a room that has a dehumidifier set at 50%. This is more for people than wood.
Put it out of any direct airflow from a vent or a fan. Don't want to dry the paper
Every day for about 5 days I swap the bags for two dry ones and set the wet ones aside to dry and use the following day
If I see any mold on the bowls I wipe them with straight Clorox( it does not bleach the wood) and discard those bags.
After 5 days the bags are dry. At this point I put the bagged bowl on a shelf for 3-4 months
Then I take the bowl out if the bag and put it on the shelf for 2 months.
I check the moisture content periodically and any bowl under 10% goes on the dry ready to turn shelf.
Sometimes they are ready in 4 months.

I usually store the bowls in bags on their side standing on the rim leaning against a wall or something.

This works well for someone who does just a few bowls anyone doing a lot of bowls can't spend the time on bags.
I like the bagging because bowls will be dry in 4-6 months. When I used to use anchor seal it was usually 8-12 months to get a dry bowl. The anchor seal was a one time deal as opposed to changing bags 4-5 times.


Al

 

[Hu Lowery]

not really intentionally bird dogging behind you

I am in the process of drying my first few bowls in paper and have a few questions.

1. I bought kraft paper on a roll from Home Depot. Any issue with that. It's about the weight of a paper grocery bag
2. I have them sitting in my basement shop. Temperature in the shop approx 66 degrees. I could also put them in a solid concrete room (floor, walls and ceiling). Would that be better because its a bit cooler and a little higher humidity?
3. I don't have a fan blowing? Is air movement more that the normal air in a house okay or having a fan better?
4. Kind of surprised but bowls started out at 35% and after 10 days only down to 25%. Not sure why I'm surprised since Ive never done this before but thought they would dry quicker. I have them down to approx 3/8 thick with the plan of finished thickness of 1/4 inch after final shape and sand.

Any help would be appreciated

Scott,

Others with more experience than I have drying wood and in more similar climates to yours can give far better advice there than I can, Al's is solid but there are multiple ways to dry wood and a little experimentation involved to find what works for your exact conditions. I'm glad you asked about the masking paper, easier for me to come by kraft paper than bags too.

What has me posting is the dimensions you gave for bowl thickness. Normal rough thickness of a bowl that you are planning to second turn is ten percent of diameter, or for really big bowls it is rare to need to go over an inch or inch and a half thick. Under twelve inches sticking with ten percent is pretty safe. Unless you have a typo turning bowls to 3/8" thick and hoping to clean up at 1/4" thick is very unlikely to happen starting at the moisture contents you indicate and drying down to ten or twelve percent. That is only allowing one-eighth inch total out of roundness. You don't indicate bowl size but even small ones tend to wander more than that.

Hopefully 3/8 is a typo but if you are down to 3/8" thick already I suggest going ahead and finish turning these bowls ASAP and let them warp after turning. Start a new batch of blanks drying following the ten percent rule to second turn.

As mentioned in my reply to your other thread, wood turning ain't near about my area of expertize, make sure people with more experience agree with my thoughts before following my advice!

Might mention diameter and type of wood you are turning so others can tailor their advice to what you are working with.

Hu

 

[dbonertz]

The quick answer is do what you are doing to see if it works in your climate, drying space conditions and method. Many ways to dry wood. Don't use a fan they may dry to quickly and surface check. Fans are used in kilns but the humidity level is much higher and controlled in the kiln. If you rough a lot of bowls then a shelf in the concrete room may be perfect (don't bag these most likely). You really have to play around with different methods to find what is easiest for you with the best results.

I agree with Hu on twice turn bowls at 3/8" thick you may have to much warping to get what you are hoping for which again can vary from species to species. 3/4" thick would most likely work under most sizes and species but 10% is generally the accepted thickness.

Good luck,

Dale

 

[hockenbery]

Hu pointed out the 10% rule of thumb for drying face grain bowls is important.

Most woods in North America shrink around
5% radially ( Center to bark edge
10% tangentially ( around the growth rings)
0% vertically ( Roots to leaves) ( this is what makes timber frame construction work with green wood)

I posted these two crude drawings of dried bowl cross section in another post.
They show what happens with a 10% shrinkage
The one on the left Is a cross section in the middle of the bowl parallel to the grain
The one on the right is the cross section perpendicular to the grain

In the first the only shrinkage is radial
In the second both occur but tangential is at it maximum in the bowl

In this example the 10" diameter bowl 5" high with a 1" wall thickness will dry to a little less than 10"diameter in the grain axis with an inside diameter about 8" wall thickness about an 1"
In the perpendicular direction it will dry to a diameter of about 9" , inside diameter about 7.2" wall thickness about .9"

From this 1" thick bowl you can expect to be able to turn a finished bowl with at most a 1/2" wall thickness
Most of our hardwoods shrink less than the example.

Al

 

[R Henrickson]

For a period I roughed out bowls, dried them, and then second-turned. Most of the time, I turn to finish. I've mainly used paper bags for drying, whether rough-outs or final. Especially in the early stages of drying, changing the bags is a very good idea. Wrapping in paper comparable to paper bags should make no difference, though you should probably try for a single thickness. You can also use cardboard boxes. In the last several days, I've turned a couple of large bowls which were too large for bags and I had no large sheets of paper (I suppose I could have used newspaper), so I put them into shipping boxes left over from Christmas.

 

[Bill Weaver]

Scott
The above is all very good advise.. I think we live close enough to have about the same temps and humidity, but this winter has been very different. So the system might change once weather straightens out. I have tried the bag thing and it done okay that was last summer, this winter not so good. So you see climate has all the bearings in drying to make us happy for second turnings.
I tried something that at least works for me. I bought anchor seal from Woodcraft and apply to my rough cuts set them up and let dry. That was last fall. I'm just now turning them for second time with weeelllll a little warpage but they have turned out right.
Just my 2 cents worth and hope this will help you.😀

 

[robo hippy]

Well, the difficult part is that no two pieces will dry the same way. Some move a lot, others not. There is no exact science to each species. Some split just because, some are very stable. Generally, you need to round over the bowl rims, as cracks like to start there. For twice turning, yours may be a little thin, so you may end up with some nice warped bowls, which are my favorites. I didn't find the paper bag all that effective with madrone, which is a wood that requires a lot of 'special' care. A 22 inch diameter bowl dried to 25 by 17 inches, so no amount of thickness would have let it be twice turned. At least wrap the outside of the bowl, and cover the rim. Have them down on the floor, and no moving air or sun light. Then it is a wait and see. Some use plastic bags which need to be turned inside out every day or two to release the condensation. Some coat the entire bowl in sealer Some coat just the end grain. Having them on the concrete floor is good, higher humidity there. I have been taking my madrone pieces and putting them bottom down on the concrete. I do use plastic stretch film around the rims which helps a lot, again the rim is a vulnerable spot. Any know or defect is also very vulnerable to cracking. Your shop temps sound pretty ideal. Mike Mahoney says his wine cellar is perfect conditions.

robo hippy

 

[Breck Whitworth]

I am primarily a bowl man so what I have found that works the best is too coat my rough turned bowl completely with anchor seal then wrap in brown paper leaving the center somewhat open to the air. I do this by wrapping the paper from the bottom of the bowl then stuffing it into the center of the bowl leaving a part of the bottom open to the air. I put it down low close to the floor for a few weeks then put it on a shelf up higher to dry. After a few months I remove the paper then stack on it's edge so more air can get to it. I have very few cracks following this method. I think we all develop a method that works for us then stick to it.