Pressure v. Vacuum to Impregnate

scdiveteam

scdiveteam

Rick Geschrey
Silver Member
Hi,

I have been contemplating building a set up for impregnating wood rings and I don't think I will be using a vacuum system.

I have some experience with Hyperbaric science and I would like to make an observation. I believe that pressurization is a more effective way to impregnate wood because vacuum limits the Delta P to only 14.7 as opposed to what ever amount of overburden you can create using air pressure in a vessel.

I saw a post the other week where a glass jar was shown with a lid attached to a vacuum hose. In that jar was a can of poly with some submerged wood. With a partial vacuum this set up was supposed to suck the poly into the material that was immersed in the liquid. I don't think that is the case in that application and here is my argument based on physics.

Liquid will never create a negative pressure within a given column when it is exposed to a partial vacuum being imposed on top of it. It is impossible within the gravity here on earth.

To be more specific, a column of liquid has a positive head pressure based on it's weight that is proportional to it's depth. Atmospheric pressure at sea level is 14.7 which is the weight of the air column exerted on 1 square inch of surface area at sea level. Most pressure gauges read zero at sea level but zero is actually 14.7. ie: Gage pressure v. absolute pressure.

If a jar is in a partial vacuum and lets say the jar is one foot deep, then the pressure at the bottom of that jar is .445 pounds per sq. in. By removing the atmosphere and placing the vacuum above the liquid column you remove 14.7 psi and what you are left with is .445 absolute pressure at the bottom of the jar filled with liquid which is the specific weight of that liquid based on a 1 sq. in. foot print. So the total head pressure in the liquid is reduced from 15.14 psi to .445 absolute head pressure. This is hardly a vacuum being imposed within the liquid by the process because the .445 is still a positive reading within the liquid.

Conversely if you take the same set up and pressurize to 100 psi by injecting air into the jar, the pressure at the bottom of the liquid will increase to .445 plus 100 psi or 100.445 psi.

If the wood material in totally immersed in the liquid (some type of ballast would be added to the wood object to keep it from floating) then, the open cells of the wood would be subject to a differential or (Delta P). That would force the liquid into the wood fiber from the effects of pressurization due to the static head exerted.

Because the cellulose fiber in the wood started out a 14.7 psi at sea level and the liquid pressure at the bottom of the jar is now 100.445 there is now an 85.74 psi Delta P trying to force the poly into the wood at the bottom of the jar. Much for effective!

I am sure that some very dense woods would not impregnate as well as some softer woods but that is another subject concerning permeable membranes. The only practical thing to solve for us cue makers is how long does it take for any given wood to be saturated and at what time will the poly form a seal within the wood preventing total saturation. I would suggest that you would have better luck achieving this goal if the wood unit is cored before the process but then again, I core everything. :yeah:

Rick Geschrey
 
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I believe that you are wrong in your thinking. The negative pressure does apply throughout the liquid the same as positive pressure.

I put maple rings in an alcohol dye solution and then put it under a vacuum. The maple rings foam as the air comes out of the wood grain. When the foaming stops I remove the vacuum pump and the maple rings sink to the bottom. This happens because the liquid replaces the air in the grain and is then forced in at atmospheric pressure. (14.7 psia.) This impregnates the maple ring through and through. I believe that this might work with acrylic or sealer also if the solution is thinned enough.

The air real pressure above the liquid is added or subtracted from the pressure caused by the mass being attracted by gravity. The difference is between absolute pressure and gauge pressure.


Have you ever had the bends??? You still might have a bubble or 2 left....LOL

Kim
 
I think what makes the most sense is a combination of both.

If you vacuum the alcohol based dye, you won't ever really reach a good vacuum because the alcohol will be constantly evaporating and filling the void that you are trying to evacuate.

So, the best thing would be to evacuate the chamber with only the wood in it. In this way, you open the cells of the wood and completely remove anything that is there because it boils off.

Next, you trap the vacuum and let the dye enter the chamber. It will immediately flow into those open cells as far as it can "soak" in.

Finally, you introduce pressure. The pressure will then continue to force the dye into areas it would not otherwise reach.

Just my thoughts!
 
I think the amount of vacuum needs to be higher. Simply making it zero pressure is not enough. Even a small automotive vacuum pump used on diesel engines for braking supply about 2-3 bars of vacuum. Applying vacuum first and then introducing the dye, as Royce stated above, is a much better way to do it instead of having the dye under the same vacuum as the piece of wood the whole time.

Bob Danielson
www.bdcuesandcomix.com
 
whammo57 said:
I believe that you are wrong in your thinking. The negative pressure does apply throughout the liquid the same as positive pressure.

I put maple rings in an alcohol dye solution and then put it under a vacuum. The maple rings foam as the air comes out of the wood grain. When the foaming stops I remove the vacuum pump and the maple rings sink to the bottom. This happens because the liquid replaces the air in the grain and is then forced in at atmospheric pressure. (14.7 psia.) This impregnates the maple ring through and through. I believe that this might work with acrylic or sealer also if the solution is thinned enough.

The air real pressure above the liquid is added or subtracted from the pressure caused by the mass being attracted by gravity. The difference is between absolute pressure and gauge pressure.

Have you ever had the bends??? You still might have a bubble or 2 left....LOL

Kim
Click to expand...

Kim,

I see and understand your point and I never said the vacuum method does not work. That would be very stupid of me as I know that guys are doing this.

I am not interested in dying wood I want to impregnate a sealer.

I said "I believe that pressurization is a more effective way to impregnate wood because vacuum limits the Delta P to only 14.7 as opposed to what ever amount of overburden you can create using air pressure in a vessel".

The differential can never be more than one atmosphere in your model using a vacuum and it is true that the wood had 14.7 psi stability within it before the vacuum was applied. That is like taking the wood down to 33 feet of water when the vacuum is applied on top of the column due to this residual air content within the part that was ambient. Just because the ring sinks does not mean it is completely saturated although it may be.

By using pressure the delta expands proportional to the head pressure where the sky is the limit of your compressor psi. By placing just 89 psi over the liquid is like taking the same wood piece down to a depth of 200 feet of equivalent water pressure. That seems more efficient to me and was my point.

Royce's comment about using both vacuum and pressure may be the best way to optimize the impregnation process when using resin, I don't know.

I was a commercial diver for 30 years and used & operated hyperbaric chambers and had 30 employees on my staff and we never had a case of the bends because we followed strict operational procedures.

Real Professionals don't get the bends unless they make a mistake! Some professions don't allow room for mistakes without dramatic consequences. That's like a roofer falling off a roof. You can walk to the edge but if your not real careful on the edge, there is a risk you can fall.

To sum things up I would like to make the point that when I build my vessel, I will kept an open mind in my testing and observations. I don't expect you to change what you are doing either, I was just putting out some food for thought.

Rick Geschrey
 
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RBC said:
I think what makes the most sense is a combination of both.

If you vacuum the alcohol based dye, you won't ever really reach a good vacuum because the alcohol will be constantly evaporating and filling the void that you are trying to evacuate.

So, the best thing would be to evacuate the chamber with only the wood in it. In this way, you open the cells of the wood and completely remove anything that is there because it boils off.

Next, you trap the vacuum and let the dye enter the chamber. It will immediately flow into those open cells as far as it can "soak" in.

Finally, you introduce pressure. The pressure will then continue to force the dye into areas it would not otherwise reach.

Just my thoughts!
Click to expand...

we have a winner.

bill
 
RBC said:
I think what makes the most sense is a combination of both.

If you vacuum the alcohol based dye, you won't ever really reach a good vacuum because the alcohol will be constantly evaporating and filling the void that you are trying to evacuate.

So, the best thing would be to evacuate the chamber with only the wood in it. In this way, you open the cells of the wood and completely remove anything that is there because it boils off.

Next, you trap the vacuum and let the dye enter the chamber. It will immediately flow into those open cells as far as it can "soak" in.

Finally, you introduce pressure. The pressure will then continue to force the dye into areas it would not otherwise reach.

Just my thoughts!
Click to expand...

I agree with you totally.... The way I do it, the alcohol dye totally penetrates a maple ring that is .120 in thick.

I believe the same would happen with an acrylic solution using acetone. Acetone might not be good for the vacuum pump. I am going to try it as I have an acetone/plexiglass solution. I am going to see if a maple ring impregnated with this will remain cleaner when it is next to cocobolo. Right now I use a sprayed water based sealer and it seems to work well.

Kim
 
scdiveteam said:
Kim,

I see and understand your point and I never said the vacuum method does not work. That would be very stupid of me as I know that guys are doing this.

I am not interested in dying wood I want to impregnate a sealer.

I said "I believe that pressurization is a more effective way to impregnate wood because vacuum limits the Delta P to only 14.7 as opposed to what ever amount of overburden you can create using air pressure in a vessel".

The differential can never be more than one atmosphere in your model using a vacuum and it is true that the wood had 14.7 psi stability within it before the vacuum was applied. That is like taking the wood down to 33 feet of water when the vacuum is applied on top of the column due to this residual air content within the part that was ambient. Just because the ring sinks does not mean it is completely saturated although it may be.

By using pressure the delta expands proportional to the head pressure where the sky is the limit of your compressor psi. By placing just 89 psi over the liquid is like taking the same wood piece down to a depth of 200 feet of equivalent water pressure. That seems more efficient to me and was my point.

Royce's comment about using both vacuum and pressure may be the best way to optimize the impregnation process when using resin, I don't know.

I was a commercial diver for 30 years and used & operated hyperbaric chambers and had 30 employees on my staff and we never had a case of the bends because we followed strict operational procedures.

Real Professionals don't get the bends unless they make a mistake! Some professions don't allow room for mistakes without dramatic consequences. That's like a roofer falling off a roof. You can walk to the edge but if your not real careful on the edge, there is a risk you can fall.

To sum things up I would like to make the point that when I build my vessel, I will kept an open mind in my testing and observations. I don't expect you to change what you are doing either, I was just putting out some food for thought.

Rick Geschrey
Click to expand...



Rick,

I was only kidding about the bends.... (probably wasn't really funny anyways) Your avatar told me you were a diver.

I believe that the commercial people that stabilize wood with resin do evacuate and then use high pressurize to get complete saturation.

Somebody else on the forum does use vacuum to impregnate maple with lacquer sealer. The 14.7psi does pressurize the solution into the maple somewhat after releasing the vacuum.

As the cover sealed but is not secured on my vessel, I can only do vacuum and not pressure. A paint pot would be ready made for this operation. I will watch garage sales for a small cheap one.

Kim
 
interesting concept rick. i have a question, would it be easier to draw fluid into a open ended straw or push it thru a closed ended straw? a vacum system would be based on a concept of "remove and replace" (and i think you know that). the pressure system your describing (as i understand it) puts both air and liquid at the same pressure. it would seem your are attempting to condense the product as there is no where for the air in the wood to go (no delta p,no flow). it may be an interesting apraoch if you could somehow create a seal around the outside of one end and expose it to atmosphere. you would get a delta p this this way. the real question is how fast can you create a vacum or head pressure to overcome the cure time of poly. with respect to your experience, this is a very "laymans" observation and was intrigued with your proposal. may you have good luck with the experiment.........andy
 
I've played around with this quite a bit over the last couple years. The best method is first vacuum, then pressure, sometimes a couple of cycles of this depending on the density of the woods. I do not recommend using any thing with a flamable solvent in it, as the higher the vaccum, the lower the flashpoint / boiling point of the liquid. An explosion could happen. Plus the acetone and others like it will eat out every seal in your vacuum pump. There are filters you can put inline, but it only delays it from happening.
I use a product call Ultraseal. It is a Thermo-cure polymer solution that works really good, but the cost is not cheap. It is designed for this type of thing. It needs to be put in an oven so that the inner temp of the blank reaches 195 degrees for no less than 10 minutes. As with any chemical solution care is needed when handling, etc.
The above link from Cuecaps for the penturners site has a lot of info on the subject.
Hope this helps.
Dave
 
avscue said:
interesting concept rick. i have a question, would it be easier to draw fluid into a open ended straw or push it thru a closed ended straw? a vacum system would be based on a concept of "remove and replace" (and i think you know that). the pressure system your describing (as i understand it) puts both air and liquid at the same pressure. it would seem your are attempting to condense the product as there is no where for the air in the wood to go (no delta p,no flow). it may be an interesting apraoch if you could somehow create a seal around the outside of one end and expose it to atmosphere. you would get a delta p this this way. the real question is how fast can you create a vacum or head pressure to overcome the cure time of poly. with respect to your experience, this is a very "laymans" observation and was intrigued with your proposal. may you have good luck with the experiment.........andy
Click to expand...

The pressure method is used a lot when casting. It will compress the air bubbles to be so small that they can't be seen. A casting epoxy or similar type stuff works great with it, as it will harden in a set timeframe while the pressure is still applied. Using only pressure as in Rick's idea, with a non self curing liquid, a lot of the fluid will gush back out as soon as the pressure is released, and the the penetration will not be a deep. A vacuum method virtually makes the wood blank a sponge, which will suck in the fluids, and retain a very high percentage when it's removed for drying. The key is to dry or set as fast as possible to retain as much of the stabilizers as possible.
Dave
 
scdiveteam said:
Hi,

I have been contemplating building a set up for impregnating wood rings and I don't think I will be using a vacuum system.

I have some experience with Hyperbaric science and I would like to make an observation. I believe that pressurization is a more effective way to impregnate wood because vacuum limits the Delta P to only 14.7 as opposed to what ever amount of overburden you can create using air pressure in a vessel.

I saw a post the other week where a glass jar was shown with a lid attached to a vacuum hose. In that jar was a can of poly with some submerged wood. With a partial vacuum this set up was supposed to suck the poly into the material that was immersed in the liquid. I don't think that is the case in that application and here is my argument based on physics.

Liquid will never create a negative pressure within a given column when it is exposed to a partial vacuum being imposed on top of it. It is impossible within the gravity here on earth.

To be more specific, a column of liquid has a positive head pressure based on it's weight that is proportional to it's depth. Atmospheric pressure at sea level is 14.7 which is the weight of the air column exerted on 1 square inch of surface area at sea level. Most pressure gauges read zero at sea level but zero is actually 14.7. ie: Gage pressure v. absolute pressure.

If a jar is in a partial vacuum and lets say the jar is one foot deep, then the pressure at the bottom of that jar is .445 pounds per sq. in. By removing the atmosphere and placing the vacuum above the liquid column you remove 14.7 psi and what you are left with is .445 absolute pressure at the bottom of the jar filled with liquid which is the specific weight of that liquid based on a 1 sq. in. foot print. So the total head pressure in the liquid is reduced from 15.14 psi to .445 absolute head pressure. This is hardly a vacuum being imposed within the liquid by the process because the .445 is still a positive reading within the liquid.

Conversely if you take the same set up and pressurize to 100 psi by injecting air into the jar, the pressure at the bottom of the liquid will increase to .445 plus 100 psi or 100.445 psi.

If the wood material in totally immersed in the liquid (some type of ballast would be added to the wood object to keep it from floating) then, the open cells of the wood would be subject to a differential or (Delta P). That would force the liquid into the wood fiber from the effects of pressurization due to the static head exerted.

Because the cellulose fiber in the wood started out a 14.7 psi at sea level and the liquid pressure at the bottom of the jar is now 100.445 there is now an 85.74 psi Delta P trying to force the poly into the wood at the bottom of the jar. Much for effective!

I am sure that some very dense woods would not impregnate as well as some softer woods but that is another subject concerning permeable membranes. The only practical thing to solve for us cue makers is how long does it take for any given wood to be saturated and at what time will the poly form a seal within the wood preventing total saturation. I would suggest that you would have better luck achieving this goal if the wood unit is cored before the process but then again, I core everything. :yeah:

Rick Geschrey
Click to expand...

May not be exactly what you are looking for but I have used one of these for years and it works fine. It is really good for soaking tips; in a few seconds you do what it may take hours just soaking in general. Just a thought and it's cheap and quick. You may be over thinking this a bit.
http://www.goodmans.net/i/3766/vacuvin-2977450-instant-marinator-with-pump.htm
 
bdcues said:
Why is this when a vacuum pump will create 2 to 3 atmospheres of vacuum?

Bob Danielson
www.bdcuesandcomix.com
Click to expand...

Bob,

I am learned in hyperbaric stuff not hypobaric but I think that no matter what you do it is impossible to devoid a space to create a perfect vacuum to remove all matter - maybe in deep space it can be done but don't quote me.

Once most of all of the matter (air) is removed from a vacuum vessel, the deed is done. A vacuum pump can't pull out matter that is not there and even the most powerful muti-staged vac pumps in the world will never quite finish the job of removing one atmosphere.

Rick
 
the gauges for testing the vacuum pump on diesel motors measure in bars or atmospheres. Typically the pumps produce over 2 bars - atmospheres - of vacuum, needed because diesels do not make manifold vacuum to run the brake system. As I remember the gauge we used went to something like 3 bars? Someone still working with diesels could tell you. I don't know about deep space but I do know that it takes more than 14.7" vacuum to make the car stop.

Bob
 
Hi Bob,

I kinda thought that you may be referring to bar measures on the other post. It does get confusing so I just did a little research to refresh my thoughts in this area.

http://www.sensorsone.co.uk/news/26...gative-gauge-or-absolute-pressure-ranges.html

The typical absolute pressure range for measuring vacuum pressures is 0 to 1 bar absolute.

Again I am not experienced in dealing with vacuum issues but I am sure this site will make things clear.

Where is the physics professor when you need them.:help:

Rick G
 
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