Stabilization- Use of Autoclave???

[Druid]

Has anyone used an autoclave to polymerize stabilized wood instead of an oven? I've been thinking if one could be used. One problem I think I see is most autoclave's are designed to heat around 250 at 20 PSI (which is ok) but the heat/pressure is steam generated. The heat is usually generated by a water heating element and will not work without water.

My initial thoughts are steam + wood is BAD. Steam + Ultraseal or Resinol 90C = big mushroom cloud and :doctor:

But maybe I'm totally wrong, your experience & thoughts would be appreciated. I'd also like to know if you have used an autoclave for something other than sterilizing equipment.

 

[DozerMite]

The autoclaves we use at work are adjustable for the temp. and pressure. The steam is in a chamber that surrounds the inside pot. In other words, it's double walled so the steam isn't inside with the material, just in a chamber around it.

 

[Jim Smith]

You might consider a vacuum oven like this http://cgi.ebay.com/VWR-Scientific-...34.c0.m14.l1262&_trkparms=|301:0|293:3|294:30 I've bought several items from these guys including a vacuum pump and vacuum oven and they're great to do business with. I have not had a chance to use the vacuum oven yet, but the way it works is that you hook up your vacuum pump, pull the vaccum for the desired amount of time, then simpy turn on the oven to cook in the stabilizer. Just a thought...

Jim Smith

 

[Constant Laubscher]

Heat does not transfer in a vacuum!

You might consider a vacuum oven like this http://cgi.ebay.com/VWR-Scientific-...34.c0.m14.l1262&_trkparms=|301:0|293:3|294:30 I've bought several items from these guys including a vacuum pump and vacuum oven and they're great to do business with. I have not had a chance to use the vacuum oven yet, but the way it works is that you hook up your vacuum pump, pull the vaccum for the desired amount of time, then simpy turn on the oven to cook in the stabilizer. Just a thought...

Jim Smith

 

[Druid]

Heat does not transfer in a vacuum!

Interesting, not to start a debate.. Lord knows I'm not a chemical engineer or physicist but the only way heat can transfer through a vacuum is by radiation. Hot objects radiate energy, mostly in the infrared portion of the electromagnetic spectrum, and whatever is on the other side of the vacuum can absorb the infrared light and heat up. Radiation isn't very strong unless the hot object is extremely hot, which is why in general vacuum is a very good insulator.
The other two methods of heat transfer, conduction and convection, don't come into play here, You can't have conduction without some matter in between, which the vacuum doesn't have. Convection is heat transfer through air currents, and there's no air in a vacuum.
Thermoses take advantage of these insulating properties of a vacuum by sealing vacuum in a glass sheath.

Thanks for the info all, I'll just have to give it a try. I'll provide some feedback if anyone has interest.

 

[Fred]

Heat does not transfer in a vacuum!

I hate to completely disagree with you on this issue, but ...

For example ...

Doesn't heat transfer through the 93+ million miles the vacuum of space from the Sun to heat the Earth. Go to the beach and prove otherwise ... and IF I am wrong give NASA a telephone call and save the taxpayers and the space industry zillions of dollars on the development of heat/cold thermal suits!

Doesn't heat get emitted from the vacuum inside a light bulb to your fingers when you touch it and it has been on for several seconds/minutes? Touch one and let us know how your fingers make out ...

You can pull a vacuum on a container, seal the container, then place that container inside an oven. Given a bit of time whatever is inside that container does get as hot as the oven temp is set to.

In other words heat does indeed transfer itself through a vacuum and it does so rather efficiently. :biggrin:

 

[ldb2000]

I hate to completely disagree with you on this issue, but ...

For example ...

Doesn't heat transfer through the 93+ million miles the vacuum of space from the Sun to heat the Earth. Go to the beach and prove otherwise ... and IF I am wrong give NASA a telephone call and save the taxpayers and the space industry zillions of dollars on the development of heat/cold thermal suits!

Doesn't heat get emitted from the vacuum inside a light bulb to your fingers when you touch it and it has been on for several seconds/minutes? Touch one and let us know how your fingers make out ...

You can pull a vacuum on a container, seal the container, then place that container inside an oven. Given a bit of time whatever is inside that container does get as hot as the oven temp is set to.

In other words heat does indeed transfer itself through a vacuum and it does so rather efficiently. :biggrin:

HEAT does NOT transfer in a vacuum
It is not heat from the sun that you feel at the beach , it's the solar radiation (infrared light energy) that heats the earths atmosphere which you feel through convection of the air . The light bulbs glass envelope is hot because the radiation is heating the molecules in the glass and something in a container that is under a vacuum gets hot through conduction from the container it is in , and infrared radiation from the heated container itself .

 

[Constant Laubscher]

Inner Workings of a Thermos

One way to build a thermos-like container would be to take a jar and wrap it in, for example, foam insulation. Insulation works by two principles. First, the plastic in the foam is not a very good heat conductor. Second, the air trapped in the foam is an even worse heat conductor. So conduction has been reduced. Because the air is broken into tiny bubbles, the other thing foam insulation does is largely eliminate convection inside the foam. Heat transfer through foam is therefore pretty small.

It turns out that there is an even better insulator than foam: a vacuum. A vacuum is a lack of atoms. A "perfect vacuum" contains zero atoms. It is nearly impossible to create a perfect vacuum, but you can get close. Without atoms you eliminate conduction and convection completely.
What you find in a thermos is a glass envelope holding a vacuum. Inside a thermos is glass, and around the glass is a vacuum. The glass envelope is fragile, so it is encased in a plastic or metal case. In many thermoses you can actually unscrew and remove this glass envelope.
A thermos then goes one step further. The glass is silvered (like a mirror) to reduce infrared radiation. The combination of a vacuum and the silvering greatly reduces heat transfer by convection, conduction and radiation.
So why do hot things in a thermos ever cool down? You can see in the figure two paths for heat transfer. The big one is the cap. The other one is the glass, which provides a conduction path at the top of the flask where the inner and outer walls meet. Although heat transfer through these paths is small, it is not zero.
Does the thermos know whether the fluid inside it is hot or cold? No. All the thermos is doing is limiting heat transfer through the walls of the thermos. That lets the fluid inside the thermos keep its temperature nearly constant for a long period of time (whether the temperature is hot or cold).

 

[RBoutin]

Jim, I've posed your question to the guys in the U.K. I didn't get an answer yesterday so I'm expecting on Monday.

Has anyone used an autoclave to polymerize stabilized wood instead of an oven? I've been thinking if one could be used. One problem I think I see is most autoclave's are designed to heat around 250 at 20 PSI (which is ok) but the heat/pressure is steam generated. The heat is usually generated by a water heating element and will not work without water.

My initial thoughts are steam + wood is BAD. Steam + Ultraseal or Resinol 90C = big mushroom cloud and :doctor:

But maybe I'm totally wrong, your experience & thoughts would be appreciated. I'd also like to know if you have used an autoclave for something other than sterilizing equipment.

 

[jedgerton]

It's been a while since I've studied this but what I remember is there are 3 ways heat transfer occurs:

1. Radiant
2. Convection
3. Conduction

Radiant heat transfers very well through a vacuum whereas convection isn't possible. The basic idea of most insulation is to eliminate the convection component by either trapping air or surrounding something by a vacuum.

When a reflective material is used, its intended to reflect radiant heat.

John

 

[Druid]

UPDATE

Ok, I first ran a test with a couple of buckeye burl blanks (nice and dry) with them in the autoclave chamber to see if in fact they collected any moisture in the process. I weighed the blanks first and borrowed a sensitive humidity probe from my neighbor. After reaching 190 at 20 PSI for 20 mins I slowly released the pressure and removed the blanks. They were hot to the touch, cut one in half and the core temp was at 193, and the blanks didn't seem moist by touch. The weight picked up a gram but the moisture probe displayed slightly over 8%. The blanks did cool and dry within 30 mins bringing the moisture down to less than 1%. Interesting data but really tells me little.

Sooooo.... off to Quantico where I ran an extension cord out from a building (a place we know as little Beirut) and placed 20 blanks stabilized with Ultraseal into the autoclave and cranked the puppy up to 210 at 20 PSI and held that for 30 min's. There was no propulsion, mushroom cloud over the horizon, or bio gas release that required a MOP suit. I removed the blanks and will now turn in a few days to see the results. More to follow next week, look forward to hearing what the chemical engineers have to say at Ultraseal.

 

[titan2]

You might consider a vacuum oven like this http://cgi.ebay.com/VWR-Scientific-...34.c0.m14.l1262&_trkparms=|301:0|293:3|294:30 I've bought several items from these guys including a vacuum pump and vacuum oven and they're great to do business with. I have not had a chance to use the vacuum oven yet, but the way it works is that you hook up your vacuum pump, pull the vaccum for the desired amount of time, then simpy turn on the oven to cook in the stabilizer. Just a thought...

Jim Smith

The price is great.....but, boy that shipping will kill you!!!!

Barney