Casting Jumping Cholla

Question: I've been looking at Alumilite and reading various other forums on casting, and I can't quite get my head wrapped around the differences and preferences (for our use) of the Water Clear, Clear and Amazing Clear versions. I'll leave out the "Clear Slow" for now.

Any ruminations on this?
 
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Clear slow is what I use. It’s made for turning and has a longer open time. Gives you time to mix and pour and get it in your pressure tank before starting to cure. Clear slow gives you a 12 minute open time. Just be sure any wood material
You are casting is completely dry or you will get bubbles where resin contacts the wood.
 
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I use liquid dyes and you need some colored or metallic powders to give the resin depth. Just plain dye is translucent.
 
TMAC said:
Clear slow is what I use. It’s made for turning and has a longer open time. Gives you time to mix and pour and get it in your pressure tank before starting to cure. Clear slow gives you a 12 minute open time. Just be sure any wood material
You are casting is completely dry or you will get bubbles where resin contacts the wood.
Click to expand...
Would there be time to put the cast part into a vacuum first and then transfer to the pressure pot? Not that I'd necessarily do that, just wondering about any "gel" issue during the open time.
 
If you have any questions you can pm me and I’ll be glad to help any way I can.
 
You would use a vacuum chamber if you were using stabilizing resin. Pressure is what you would use for casting resin. Two completely separate processes. I do both on blanks I turn. Blanks that are stabilized in a vacuum chamber also need to be completely dry. I usually put mine in a low temp oven until moisture level is near 0%. Stabilize first if you intend to. Then after your stabilizing resin has been cured in an oven they will be ready to cast. Wait until blanks are cool before casting. I usually cast the next day.
 
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  • Thread Starter Thread Starter
  • #51
I have never used vacuum on Alumilite resin to degas prior to potting at pressure and have had great results. Generally, there’s so much free air space in dry wood that degassing epoxy prior to pouring doesn’t make sense.

In theory, it would make more sense to pull a vacuum on the wood/ mold cavity and have some type of apparatus to introduce epoxy back into the wood/mold while venting, not allowing air to enter, but just the resin until you reach atmospheric pressure. Then switch over to pressure.

commercial casting process can use vacuum bags and an autoclave to vary pressure and temperature. But again, pure pressure works pretty well if you prep the wood. Of course, you will have some small bubbles from time to time but those come from the wood and not epoxy.

Someone mentioned earlier, and I agree, that the Cadillac way to go would be to apply a lot more pressure (500 or 1000 psi). This way epoxy is driven deeper into the wood. I have experimented with pressure stabilization at up to 500 psi, but the juice wasn’t worth the squeeze 😂
 
I've been thinking about this ....

In theory, it would make more sense to pull a vacuum on the wood/ mold cavity and have some type of apparatus to introduce epoxy back into the wood/mold while venting, not allowing air to enter, but just the resin until you reach atmospheric pressure. Then switch over to pressure.
Click to expand...

1. Drill and tap a hole in the lid of my vac tank, or at least very high up on the side. Thread in a small pipe nipple and seal it.

2. On the inside, thread on a short length of flexible tubing that can be positioned inside the mold or resin container. On the outside, thread on a full port ball valve rated for the vacuum.

3. To the inlet side of the valve thread on a length of tubing with a funnel shape on the end.

Then, set up my mold inside the vac tank, position the flexible tubing so it's inside the mold. Close up the tank and suck a vacuum. Mix up the resin and begin filling the flexible tube outside the vac tank, making sure I have a full tube and reservoir of resin ready. Once the vacuum is achieved, open the full port ball valve and feed resin through the tubing into the mold. Stop before allowing any air to enter beyond the ball valve. Let the resin penetrate under vacuum, pouring additional resin into the mold if needed. Then, release the vacuum and switch to pressure mode, if you have that capability and finish the cure.

One problem would be cleaning out the ball valve and tubing sufficiently so it would work the next time. But the only air introduced would be the air entrained in the resin. Theoretically, that air would bubble out once the resin entered the vacuum. Foaming would be something you'd have to watch out for.
 
There is no reason not to just immerse your wood into resin so that the resin level is above the top surface of the wood and the wood is secured so that it doesn't float. Resin level must stay above the top of the wood during this part, so any mold must accommodate that need.
  1. Close the chamber and apply the vacuum. The air inside the wood (under resin) will expand and the bubbles will rise to the surface of the resin.
  2. Leave vacuum on for several minutes (use slow curing resin) or until there are no more bubbles coming to the surface. (You may need X-ray eyes for this ... or a clear lid :ponder: ... or experience)
  3. Note: the air pressure under this full vacuum is nominally 0 psi.
  4. Then, slowly release the vacuum, i.e., allow outside air to re-enter the chamber.
  5. As the air returns to the chamber, you are essentially applying 14.7psi (atmospheric pressure) to the resin immersed wood.
  6. Now, apply additional pressure via your air compressor.
  7. Proceed as normal.

There is no reason to try to add the resin after pulling the vacuum. No needed complications.

The switch from vacuum to venting to applying external air pressure might require an extra valve; or not; if you use matched Quick Disconnects for the vacuum and air lines. Just swap from one to the other.

What's really happening: After immersing your wood in resin and placing it into the chamber you are then pulling a vacuum on everything in the chamber.
  1. Under full vacuum, any air in the resin expands into bubbles and will float upward to the surface of the resin and pop.
  2. Any air in the wood voids will expand into bubbles and float upward to the surface of the resin and pop.
  3. Eventually, all the air is pulled out of the resin and out of the wood. No more bubbles.
  4. Any remaining voids in the wood will be full of … nothing … the voids will be under full vacuum (0 psi).
  5. Now, when you fully release the vacuum (do it slowly) returning air to the chamber, you are then applying 14.7psi to the resin surrounding the wood, forcing it into all the voids.
  6. Since the air was sucked out of the voids, they are at 0 psi and will draw in the resin being pushed at 14.7psi from the outside to fully fill the voids.
  7. Adding external pressure after that will further compress any residual air per the usual process.
 
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Steelart99 said:
There is no reason not to just immerse your wood into resin so that the resin level is above the top surface of the wood and the wood is secured so that it doesn't float. Resin level must stay above the top of the wood during this part, so any mold must accommodate that need.
  1. Close the chamber and apply the vacuum. The air inside the wood (under resin) will expand and the bubbles will rise to the surface of the resin.
  2. Leave vacuum on for several minutes (use slow curing resin) or until there are no more bubbles coming to the surface. (You may need X-ray eyes for this ... or a clear lid :ponder: ... or experience)
  3. Note: the air pressure under this full vacuum is nominally 0 psi.
  4. Then, slowly release the vacuum, i.e., allow outside air to re-enter the chamber.
  5. As the air returns to the chamber, you are essentially applying 14.7psi (atmospheric pressure) to the resin immersed wood.
  6. Now, apply additional pressure via your air compressor.
  7. Proceed as normal.

There is no reason to try to add the resin after pulling the vacuum. No needed complications.

The switch from vacuum to venting to applying external air pressure might require an extra valve; or not; if you use matched Quick Disconnects for the vacuum and air lines. Just swap from one to the other.

What's really happening: After immersing your wood in resin and placing it into the chamber you are then pulling a vacuum on everything in the chamber.
  1. Under full vacuum, any air in the resin expands into bubbles and will float upward to the surface of the resin and pop.
  2. Any air in the wood voids will expand into bubbles and float upward to the surface of the resin and pop.
  3. Eventually, all the air is pulled out of the resin and out of the wood. No more bubbles.
  4. Any remaining voids in the wood will be full of … nothing … the voids will be under full vacuum (0 psi).
  5. Now, when you fully release the vacuum (do it slowly) returning air to the chamber, you are then applying 14.7psi to the resin surrounding the wood, forcing it into all the voids.
  6. Since the air was sucked out of the voids, they are at 0 psi and will draw in the resin being pushed at 14.7psi from the outside to fully fill the voids.
  7. Adding external pressure after that will further compress any residual air per the usual process.
Click to expand...
Except up where you live it's more like 13.9psi
 
Steelart99 said:
There is no reason not to just immerse your wood into resin so that the resin level is above the top surface of the wood and the wood is secured so that it doesn't float. Resin level must stay above the top of the wood during this part, so any mold must accommodate that need.
  1. Close the chamber and apply the vacuum. The air inside the wood (under resin) will expand and the bubbles will rise to the surface of the resin.
  2. Leave vacuum on for several minutes (use slow curing resin) or until there are no more bubbles coming to the surface. (You may need X-ray eyes for this ... or a clear lid :ponder: ... or experience)
  3. Note: the air pressure under this full vacuum is nominally 0 psi.
  4. Then, slowly release the vacuum, i.e., allow outside air to re-enter the chamber.
  5. As the air returns to the chamber, you are essentially applying 14.7psi (atmospheric pressure) to the resin immersed wood.
  6. Now, apply additional pressure via your air compressor.
  7. Proceed as normal.

There is no reason to try to add the resin after pulling the vacuum. No needed complications.

The switch from vacuum to venting to applying external air pressure might require an extra valve; or not; if you use matched Quick Disconnects for the vacuum and air lines. Just swap from one to the other.

What's really happening: After immersing your wood in resin and placing it into the chamber you are then pulling a vacuum on everything in the chamber.
  1. Under full vacuum, any air in the resin expands into bubbles and will float upward to the surface of the resin and pop.
  2. Any air in the wood voids will expand into bubbles and float upward to the surface of the resin and pop.
  3. Eventually, all the air is pulled out of the resin and out of the wood. No more bubbles.
  4. Any remaining voids in the wood will be full of … nothing … the voids will be under full vacuum (0 psi).
  5. Now, when you fully release the vacuum (do it slowly) returning air to the chamber, you are then applying 14.7psi to the resin surrounding the wood, forcing it into all the voids.
  6. Since the air was sucked out of the voids, they are at 0 psi and will draw in the resin being pushed at 14.7psi from the outside to fully fill the voids.
  7. Adding external pressure after that will further compress any residual air per the usual process.
Click to expand...
does the resin not behave differently for cure time and or hardness upon curing under these circumstances? some of the compnants will evaporate and be separated by this process, i would think. i have heard of plenty of totally foamed up resins cured in a frothy mass. but i could be mistaken

hence the reasoning behind stabilizing, then casting as a second separate step?
 
Steelart99 said:
There is no reason not to just immerse your wood into resin so that the resin level is above the top surface of the wood and the wood is secured so that it doesn't float. Resin level must stay above the top of the wood during this part, so any mold must accommodate that need.
  1. Close the chamber and apply the vacuum. The air inside the wood (under resin) will expand and the bubbles will rise to the surface of the resin.
  2. Leave vacuum on for several minutes (use slow curing resin) or until there are no more bubbles coming to the surface. (You may need X-ray eyes for this ... or a clear lid :ponder: ... or experience)
  3. Note: the air pressure under this full vacuum is nominally 0 psi.
  4. Then, slowly release the vacuum, i.e., allow outside air to re-enter the chamber.
  5. As the air returns to the chamber, you are essentially applying 14.7psi (atmospheric pressure) to the resin immersed wood.
  6. Now, apply additional pressure via your air compressor.
  7. Proceed as normal.

There is no reason to try to add the resin after pulling the vacuum. No needed complications.

The switch from vacuum to venting to applying external air pressure might require an extra valve; or not; if you use matched Quick Disconnects for the vacuum and air lines. Just swap from one to the other.

What's really happening: After immersing your wood in resin and placing it into the chamber you are then pulling a vacuum on everything in the chamber.
  1. Under full vacuum, any air in the resin expands into bubbles and will float upward to the surface of the resin and pop.
  2. Any air in the wood voids will expand into bubbles and float upward to the surface of the resin and pop.
  3. Eventually, all the air is pulled out of the resin and out of the wood. No more bubbles.
  4. Any remaining voids in the wood will be full of … nothing … the voids will be under full vacuum (0 psi).
  5. Now, when you fully release the vacuum (do it slowly) returning air to the chamber, you are then applying 14.7psi to the resin surrounding the wood, forcing it into all the voids.
  6. Since the air was sucked out of the voids, they are at 0 psi and will draw in the resin being pushed at 14.7psi from the outside to fully fill the voids.
  7. Adding external pressure after that will further compress any residual air per the usual process.
Click to expand...
might work best with long cure time resin? longer than 12 minute?
 
vegas urban lumber said:
does the resin not behave differently for cure time and or hardness upon curing under these circumstances? some of the compnants will evaporate and be separated by this process, i would think. i have heard of plenty of totally foamed up resins cured in a frothy mass. but i could be mistaken

hence the reasoning behind stabilizing, then casting as a second separate step?
Click to expand...
Once mixed, the two components will not separate again as the chemical reaction has already been initiated and the combined parts become a single component. The only difference between using both vacuum and then pressure as opposed to just pressure is only some minutes under vacuum. With a relatively high viscosity material like the resin, and the minimal time under vacuum, any evaporation would be vanishingly small.

That said, there is absolutely nothing wrong with doing the two stages as you've presented them. Stabilizing and then casting under pressure. I am absolutely not denigrating that concept; I just didn't know what has been used for casting.

Frothy, foamed up resin is likely only a process issue. Vacuum needs to be brought up relatively slowly, or in steps, to avoid having a massive amount of bubbles being created quickly, popping and blowing the resin everywhere (foaming). But if the vacuum is brought up a bit slower or in steps, the bubbles have time to pop and make room for the resin to settle. As more vacuum is applied, the smaller air pockets will then swell up into bubbles and float to the surface. That is where the two step process you've described is helpful, because you can have a transparent lid on a vacuum system which allows you to monitor the bubbles created and gradually increase the amount of vacuum as bubbles are created and then pop. Follow up with pressure.

In practice, you could use a dedicated vacuum system first, where you can monitor/control the amount of vacuum. Then remove the mold/wood/wet-resin from the vacuum tank and put it into the pressure tank and then proceed on with that step. I guess I was just trying to see if this could be done within a single system.

Full Disclosure: I have never tried to cast wood but was only trying to determine the applicability of my experiences to this process. I have been intimately involved with using/testing resins and adhesives in an aerospace environment as full-time employment for over 15 years. Granted ... in my younger years.:wonky: Part of my time there included building carbon/fiberglass/Kevlar/spectra impregnated composite components for missiles, aircraft pods, etc. Our biggest autoclave was 8-ft diameter x 20-ft long to accommodate some of the parts we built. Whenever we mixed any adhesive/resins/silicone/etc., we would use vacuum to degas it before going into the pressure/heat cycles. Again, that has been my experience and it could certainly not be applicable to casting as we are discussing here.
 
vegas urban lumber said:
might work best with long cure time resin? longer than 12 minute?
Click to expand...
Cure time is probably one of the most critical aspects of casting, but you'd have to ask the guys who have actually put time into. I'm new to it.

I think I could say that a long cure time would be advantageous when trying to use both vacuum and pressure cycles. How long ... <shrug>

For that matter, the whole concept of trying to use both vacuum and pressure might be totally unnecessary. If pressure only already creates an optimal version of a casting, then adding steps is without merit.
 
  • Thread Starter Thread Starter
  • #59
Steelart99 said:
There is no reason not to just immerse your wood into resin so that the resin level is above the top surface of the wood and the wood is secured so that it doesn't float. Resin level must stay above the top of the wood during this part, so any mold must accommodate that need.
  1. Close the chamber and apply the vacuum. The air inside the wood (under resin) will expand and the bubbles will rise to the surface of the resin.
  2. Leave vacuum on for several minutes (use slow curing resin) or until there are no more bubbles coming to the surface. (You may need X-ray eyes for this ... or a clear lid :ponder: ... or experience)
  3. Note: the air pressure under this full vacuum is nominally 0 psi.
  4. Then, slowly release the vacuum, i.e., allow outside air to re-enter the chamber.
  5. As the air returns to the chamber, you are essentially applying 14.7psi (atmospheric pressure) to the resin immersed wood.
  6. Now, apply additional pressure via your air compressor.
  7. Proceed as normal.

There is no reason to try to add the resin after pulling the vacuum. No needed complications.

The switch from vacuum to venting to applying external air pressure might require an extra valve; or not; if you use matched Quick Disconnects for the vacuum and air lines. Just swap from one to the other.

What's really happening: After immersing your wood in resin and placing it into the chamber you are then pulling a vacuum on everything in the chamber.
  1. Under full vacuum, any air in the resin expands into bubbles and will float upward to the surface of the resin and pop.
  2. Any air in the wood voids will expand into bubbles and float upward to the surface of the resin and pop.
  3. Eventually, all the air is pulled out of the resin and out of the wood. No more bubbles.
  4. Any remaining voids in the wood will be full of … nothing … the voids will be under full vacuum (0 psi).
  5. Now, when you fully release the vacuum (do it slowly) returning air to the chamber, you are then applying 14.7psi to the resin surrounding the wood, forcing it into all the voids.
  6. Since the air was sucked out of the voids, they are at 0 psi and will draw in the resin being pushed at 14.7psi from the outside to fully fill the voids.
  7. Adding external pressure after that will further compress any residual air per the usual process.
Click to expand...
I’ve had wood under vacuum for hours stabilizing and air bubbles never stop. For Alumilite you have about 10 minutes. It will be a frothy cured mess.
 
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