Cooking time for pen blanks prior to stabilizing

[frankonthetis]

Good day. First post for long time lurker.

Every youTube video and discussion watched/read on this topic says to bake your blanks in a toaster oven at approximately 200-220 F for 24 hours. Little nervous at leaving a B&D toaster oven unattended overnight. Can the 24 hour cooking time be a cumulative total or does it have to be 24 consecutive hours? My preference would be heating the blanks over a couple of days to arrive at the 24 hour requirement.

Thanks for any help.

 

[MedWoodWorx]

That sounds like an overkill, what is the initial humidity level of your wood?

 

[frankonthetis]

The moisture content is probably less than 8 - 10%. The wood blanks are all spalted and have been air dried for at least 5 years indoors. The instructions for the Cactus Juice stabilizing system calls for the wood to be 0% MC before you proceed. Instructions say best way to achieve 0% MC is to bake for 24 hours.

 

[greenacres2]

I normally go 24 hours, but after having 6 buckeye burls burn in a toaster oven, I switched to a lab oven and threw the toaster oven away. Thankfully did not burn my garage. Before that fire, I had seen temp rise by more than 100 f after the burner kicked off, so should have stopped months sooner. That was a brand name oven purchased new…I shudder to think of the risk in a $5 thrift shop purchase.
Lab oven is much more efficient too, and can be had used in most of the USA.
Earl

 

[1080Wayne]

I just use my kitchen oven . Cumulative hours not as good as continuous , because the wood will start to pull moisture back in as soon as it cools down in your humid climate . Spalted wood at 8-10 % , I think 4 hours would be plenty . Zero % not super critical , either . Doubt if you will see a problem at 1-2 % but , begin stabilization ASAP after drying .

 

[ed4copies]

I have done a fair amount of stabilizing. I have a dedicated smoker that is used to dry the wood. I have, from time to time, run it all day, turned it off for the night and run it most of the second day. The most important indicator is that the wood is no longer getting lighter in weight.

So, pick ten blanks and weigh them before you start, then weigh them from time to time during the process (the SAME ten sticks). When you are weighing at 2 hour interval and the weight does not change, you are as dry as you are going to get. Take them out of the oven while still hot, if at all possible and put them in ziplock freezer bags. Weigh the bag with the wood in it and mark the total on the bag. You can put them in the stabilizing juice any time in the next few days, just make sure the bag weighs very close to what is on the bag.

I believe this is a VERY important step. My process is now giving me between 65 and 120 percent weight gain for the stabilized blanks. I attribute this success in great part to having really dry wood.

YMMV!!
Ed

 

[frankonthetis]

Thanks for your responses and suggestions Ed, 1080Wayne & greenacres2. Really have no trust in the electric appliances made these days so was hoping to be able to spread the 24 hours out over a couple of days. Have 10 blanks in the oven now but never weighed them before starting. Will weigh when bagging them tonight and start to stabilize tomorrow morning. Have 8 blanks soaking now after being in the chamber for 10 hours but they only got about 4 hours baking and still some tiny bubbles escaping when finally gave up. Will see how they turn out after the cooking tomorrow.
Will implement Ed's suggestions for next batch to be dried about weighing at the start then during the process. Will also check and see what weight is with finished blanks. Good to have a reference point for how much the resin adds to the stabilized blanks.
Thanks again for your help.

 

[its_virgil]

minimum recommended drying time is 220 degrees for 24 hours or until the blanks stop loosing weight. You can dry in sessions but the blanks will need to be stored in an air tight container so they will not take in moisture from the atmosphere.

The moisture content of the blanks will be in equilibrium with the surrounding ambient relative humidity. Blanks drying for several years may or may not be dry. Blanks stored at a relative humidity of say, 20% will not be 6 to 10% moisture content.

 

[frankonthetis]

Don, we live on an island surrounded by the ocean. Todays Weather Office records 30% relative humidity and the Weather Network says 28% relative humidity. My ready to turn blanks are mostly in drawers or boxes. Do you mean their moisture content will be higher/lower than 6-10%? Will also add maths were never a strong suit!!

 

[its_virgil]

Don, we live on an island surrounded by the ocean. Todays Weather Office records 30% relative humidity and the Weather Network says 28% relative humidity. My ready to turn blanks are mostly in drawers or boxes. Do you mean their moisture content will be higher/lower than 6-10%? Will also add maths were never a strong suit!!

My understanding is the wood blanks will be in equilibrium with the ambient relative humidity. Moisture will move from the air to the blanks and from the blanks to the air as the humidity fluctuates. So, theoretically, if the relative is 20% then your wood pen blanks will be also. The pen blanks will not be drier then the humidity in the air.
Don

 

[PatrickR]

My understanding is the wood blanks will be in equilibrium with the ambient relative humidity. Moisture will move from the air to the blanks and from the blanks to the air as the humidity fluctuates. So, theoretically, if the relative is 20% then your wood pen blanks will be also. The pen blanks will not be drier then the humidity in the air.
Don

Wood does not change nearly as fast as the humidity. My yearly average is 72% yet the wood I have stored in an uncontrolled environment measures about 12% in the summer. In the winter it will be bout 8. You would need to store wood in a humidity controlled environment for an extended period for it to equal the measurement and the more dense the wood the longer it would take.

 

[frankonthetis]

Don & PatrickR so if the relative humidity in my area is x% and the blanks are the same does that mean the MC is that same x%? If so, then how does one get to the 0% required to start stabilizing that Curtis mentions in his documentation? Do you both use moisture meters and if so what type? My pin meter from LV only goes down to 6% and understand it is inaccurate because the % reading is based on Fir wood.
Currently drying 8 rhododendrum blanks. Their total weight was 210g and after 1st drying period they were 190g [10hrs]. Yesterday morning they were at 200g and last night after another 10 hrs back to 190g. This morning the weight was 201g. The blanks were put in 2 ziploc sealed bags out of the oven. As the low weight seems to stay the same and the overnight weight gain is similar would they be considered dry enough to stabilize?

Thanks

 

[PatrickR]

1st question = no. Here is a graph that shows the relationship. Keep in mind the RH is constantly changing And wood responds slowly to this change.
for your purposes and mine when stabilizing RH is of no concern. Use as accurate a scale as possible. I had a 1g scale but broke down and got a 1/10 g. Bake until there is no more weight loss, allow it to cool and get it into the juice as soon as it cools. I don't let it sit overnight even in a ziplock.
the bake time will vary depending on the mc of the wood and the density.
2nd question = I would put it back in the oven because it has gained weight. After it hasn't changed for an hour or so it's ready.

 

[frankonthetis]

Thank you PatrickR going to print out your response and chart and post it beside my toaster oven. Have a cheap scale that does grams but will check out a better one like you did.
Thank you very much again.

 

[PatrickR]

Thank you PatrickR going to print out your response and chart and post it beside my toaster oven. Have a cheap scale that does grams but will check out a better one like you did.
Thank you very much again.

You are very welcome. One question, are you starting with air dried wood or green?

 

[wimkluck]

Does anyone have any experience with vacuum drying blanks? Water evaporates at 100 degrees Celsius. 1 bar air pressure. If you lower the pressure, the temperature at which water evaporates also changes. I also follow the method of Ed. I don't dare to leave the oven on for 24 hours. In addition, energy prices are very high.

 

[PatrickR]

Does anyone have any experience with vacuum drying blanks? Water evaporates at 100 degrees Celsius. 1 bar air pressure. If you lower the pressure, the temperature at which water evaporates also changes. I also follow the method of Ed. I don't dare to leave the oven on for 24 hours. In addition, energy prices are very high.

I did some research on it but decided I didn't want to make the chamber. I saw a video about it and it wouldn't be that hard, just wouldn't be worth it to me. A main point is you need a heat mat in the chamber.

 

[frankonthetis]

Hi PatrickR, yes all my wood blanks are air dried. Procedure is to end seal the wood blocks then leave 6+ months in woodshed or some in heated crawl space [man cave]. Then dimension to 7/8 or 3/4" sq x 5". When dimensioning green wood use either end seal from LV or latex paint and check odd one for MC. All the blanks being stabilized right now have been air dried for at least 4 years.

 

[MRDucks2]

Does anyone have any experience with vacuum drying blanks? Water evaporates at 100 degrees Celsius. 1 bar air pressure. If you lower the pressure, the temperature at which water evaporates also changes. I also follow the method of Ed. I don't dare to leave the oven on for 24 hours. In addition, energy prices are very high.

I have researched it and there is a chamber in my town that would be well suited to it but I haven't talked the owner into selling it to me, yet.

 

[duncsuss]

Does anyone have any experience with vacuum drying blanks? Water evaporates at 100 degrees Celsius. 1 bar air pressure. If you lower the pressure, the temperature at which water evaporates also changes. I also follow the method of Ed. I don't dare to leave the oven on for 24 hours. In addition, energy prices are very high.

Wim, that's not quite right.

Water boils at 100 degrees Celsius at 1 bar air pressure - it evaporates at much lower temperatures. (You can prove this easily - just leave a few drops of water in the bottom of a cup and in a day or two the cup will be dry.)

The closer the temperature gets to boiling point, the faster the liquid evaporates. Note that even at 100 Celsius, the water does not all instantaneously turn to steam - it requires additional energy (the latent heat of evaporation) to convert 100C water into 100C steam.

You are correct that reduced pressure results in a lower boiling point, and a faster rate of evaporation at temperatures below the boiling point.

 

[wimkluck]

Wim, that's not quite right.

Water boils at 100 degrees Celsius at 1 bar air pressure - it evaporates at much lower temperatures. (You can prove this easily - just leave a few drops of water in the bottom of a cup and in a day or two the cup will be dry.)

The closer the temperature gets to boiling point, the faster the liquid evaporates. Note that even at 100 Celsius, the water does not all instantaneously turn to steam - it requires additional energy (the latent heat of evaporation) to convert 100C water into 100C steam.

You are correct that reduced pressure results in a lower boiling point, and a faster rate of evaporation at temperatures below the boiling point.

You are right, there is a difference between boiling and evaporate. English is not my native language and sometimes i don't know all the words. If I read them again it will come up again. I haven't really written in English since the mid 80's.

 

[duncsuss]

English is not my native language and sometimes i don't know all the words. If I read them again it will come up again. I haven't really written in English since the mid 80's.

One thing is certain: your English is better than my Dutch will ever be