Microwaving dry wood.

[ericdockum]

Here is my question – is it ok to put items of dried wood, (dried down to bound water only), in a microwave for short periods.? Do they heat slowly, or more quickly than wet wood?

The reasons for the question are as follows.

1) Every morning I make breakfast that includes porridge in pottery bowls heated with milk in the microwave. My wife has a carefully measured amount because of her diet, I just mix mine up by eye. I also have a bit more than she does. Both bowls go in the microwave together of 3 min 30s. As the bowls are identical and the microwave has a rotating turntable it is then hard sometimes to determine whose is which. I currently put a small plastic lid off a spice pot in next to mine so I can identify it.
Every morning I think I should turn a small set of varied pieces, sort of like chessmen size, to use as personalised markers rather than use a plastic lid. Then I wonder if it would be safe….

2) I have made a small pot for shaving soap to go along with some shaver handles and shaving brush I made. I have made it to fit the dimensions of a common brand of shaving soap refill, however it is annoying when the soap spins in the dish when you are trying to get a lather. The solution is apparently to put the pot + refill in the microwave and heat for 20-30 sec. this softens the soap so in sticks in the pot.

3) One Christmas SWMBO switched the microwave on for the Xmas pud without putting the pud in the microwave. 8 mins later the glass turntable self destructed with a bang, and the plastic rotating drive and supports all melted, which wasn’t quite the christmasy smell we were looking for. Therefore there is some SWMBO resistance to me experimenting with the replacement.

I know a microwave can be used for wood drying, but how does fully dried wood react? If it has no mobile water does it still heat significantly quickly? Charring?
I guess if wood was left in for an extended period it wood have a problem, just as the glass turntable and plastic designed into our xmas microwave did eventually.

Anyone any experience?? I am not allowed to try wood drying in our microwave............

 

[finneyb]

I have dried wet wood in a microwave.
BUT I only use the defrost setting /10% power.

I wouldn't put wood in on full power, I suspect it will ignite.
You could get a indelible marker and mark your bowl.

HTH

Brian

 

[ericdockum]

i suspect a small amount of wood in with 300cc of milk + bowl in the would not heat so fast, as the water in the milk would take a lot of the energy. If overheated it might boil over and put out the wood as failsafe? The porridge doesn't get much over 70C.

The soap dish scenario might be more sensitive, with a lot less free water in the system.

 

[Bm101]

Think I'd just buy 2 different coloured porridge bowls tbh.

 

[ericdockum]

Regretfully we have a brand new kitchen with carefully matched crockery. However I am sure in the fullness of time one bowl will acquire a chip, which will then be mine and problem solved.

Did think of using a marker pen on the bottom of the bowl, but there might be a flaw with that.

 

[dickm]

You can buy paints for painting on glass; SWMBO did some decorating of a glass soap dispenser and it's still in place after a lot of water. Don't know how it survives heating, but if the bowl doesn't get above 70C, it would probably be OK. Can ask boss what the paint was called if it would help.

 

[Dalboy]

I tried drying wood in the microwave but had no success so thought I would try again forgetting to put the setting onto defrost and left it on full power set for 5 minutes not a healthy thing to do I discovered the smell of burning wood is not what you need filling your nostrils. The two saving graces to this story is One it was not in the house and Two it was my microwave for odd bits and pieces for the shed.

So my answer is no don't upset the wife there is more to life than replacing the microwave as well as the wife the second would work out cheaper in the end but microwaves are expensive :twisted: :twisted: :twisted: :lol: :lol: :lol:

 

[ericdockum]

I am still in shock from the cost of the kitchen, maybe I need a second hand microwave for experimental purposes.

Do the "odd bits and pieces for the shed" include pies at all?

Not that I would ever consider a sneaky pie in the workshop, especially as my extraction system is currently U/S.

 

[monkeybiter]

My wife regularly heats baked beans etc. in a Pyrex jug, in the microwave, with a square of kitchen roll over the top to prevent mess. Never had a problem, and she leaves stuff in for up to 5 mins at a time, full power.

 

[finneyb]

My wife regularly heats baked beans etc. in a Pyrex jug, in the microwave, with a square of kitchen roll over the top to prevent mess. Never had a problem, and she leaves stuff in for up to 5 mins at a time, full power.

.
Microwave radiation excites the water molecules, their increased movement causes the heat - kitchen roll will have very little, if any, water therefore no excitement of the molecules and therefore no heat generated in the paper.

Dry wood has 12% water content so the wood will and does get warm, even on defrost.

Brian

 

[sunnybob]

Not that I like it, but a dollop of strawberry jam in the middle of yours would solve the problem, and improve the experience at the same time.

 

[Rorschach]

How about picking up a microwave from a charity shop or car boot and use it for your experiments. Could be useful for drying wet wood etc too then. Could also use it in your workshop to heat up your coffee etc.

 

[ericdockum]

Ok, I guess my plan is as follows:

1) Forget about woodturning at breakfast time and add jam to my porridge.
2) Find a cheap second hand microwave for the Workshop
3) Fix workshop extractor so any cooking smells are removed.
4) Test said microwave for functionality with pies, may need several attempts.
5) Test wet and dry blanks with 350cc of water in microwave simulating cold porridge.
5) Test wet and dry blanks without presence of water.

Will report back.

Thanks,
Eric

 

[woodfarmer]

Why not put one pot in a saucer ?

 

[finneyb]

And, would you remember which one was on the saucer ??

 

[hawkeyefxr]

I have done this, to do it right takes a lot of time with settings low and time low as well. I tried it fast and while it did dry the wood it also tore the fibres of the wood leaving splits in the centre of the wood. A small bowl 5in dia x 2in deep held a tumbler full of water, i was astounded by the amount of water held by such a small piece of wood.

How ever just yesterday i saw a small video on Youtube about drying wood that was so simple. The guy had and old dishwasher wrapped in fibreglass, in it was a 100w bulb, he put his blanks on the shelving inside and left it for two weeks, it came out at 8%, thats perfect. He did say that it should be loaded fully all the time as just one piece of wood dried to quickly.
I think an old fridge would be perfect as it is insulated, but it will need degassing and the cooling stuff removed.

 

[ericdockum]

I was more interested in the effect of a microwave on wood that was already dried, down to bound water only. I can see that quick drying wet wood could cause damage as the hot water/steam would have to escape.

Did you try heating already kiln dried wood? That is what I would be using, small pieces in a microwave where there was already 2 bowls of free water(milk).

Following your post I perhaps need an old fridge as well as a microwave!

Thanks,
Eric.

 

[AndyT]

You could heat one bowl for half the time, then heat the other and so avoid muddling them up. The only extra time needed would be a few seconds to open and close the door. You don't really save anything by heating the two bowls together.

 

[ericdockum]

I used to do the bowls individually prior to the new kitchen crockery, as the old ones were too wide to fit 2 in at once. Since you raise the matter, I find now I can save about 20 sec heating time overall by putting the 2 together, which of course is about 2 hours over a year. (We have really exciting breakfasts!) Plus a good few door operations as well. While not a huge financial saving, operationally it is more elegant. Possibly the energy is more efficiently delivered with 2 bowls as per rotation there is 2x the number of times a bowl is under the waveguide. Google "how to measure the speed of light with chocolate" to see the effect of lack of rotation and the variance of energy delivery inside the cavity. It could well be the makeup of the bowls themselves having different makeup/iron content.

I was actually hoping that someone knew if bound water in wood microwaved differently to the excess (free) water as found in undried timber. I guess once people have dried the wood to bound water level they are done and haven't pushed further. I only raised the porridge issue as a personal example of how the question came about. I plan to try on wet and dry wood and measure the temperature rise in the wood with and without porridge in the microwave.

First I need a old microwave though.

Cheers,
Eric.

 

[AndyT]

I look forward to seeing your detailed research published in an appropriate learned journal!