Pressure Pot Suggestion Please

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magpens

magpens

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It seems that more and more of our members are learning to cast blanks.

At some point I would like to join in that activity.

I have not looked around seriously for a pressure pot, just asking for suggestions as to what other people use.

One or two of the hardware/tool stores that I frequent sell "paint pots" with a gauge on top, a lid seal, and sturdy clamps. . Is this a pressure pot ?

Another question I have relates to the use of pressure for casting as opposed to vacuum.

My intuition seems to be telling me that vacuum is what you need for casting as opposed to pressure. . Isn't vacuum the way to get bubbles out ?

I do understand the difference between pressure and vacuum and worked with both for many years in my career as an experimental physicist.

In spite of that, as I consider doing my own casting I would intuitively go for vacuum.

Happy to hear what others think.
 
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I've never done any casting myself, my experience with resin is solely based on aircraft composite structure.

If I understand what I have read properly the biggest factor that rules out vacuum is the pot life of the resins. Since they cure much more quickly than common resins used in other industries there simply isn't enough workable time for the vacuum to eliminate bubbles.

Pressure can quickly shrink bubbles small enough that they aren't an issue.

I'm sure people with experience doing this have a better explanation but that is my understanding of the reason people use pressure as opposed to vacuum.

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Thank you, Doug.

So it seems that under vacuum, there is not enough time for the (probably even enlarged) bubbles to migrate to the resin surface and burst before the curing process prevents complete migration. . Probably the resin is extremely viscous and becomes moreso as curing progresses. . I had not thought of this.
 
Well drat... Now I'll never retire in the proceeds from selling you blanks. ;)

You could probably get away with vacuum with a slow set but it's certainly very reliable to crush the air into not being a problem.

The tcp global style pot is about where I'd start. Same one is marketed by Grizzly and a few others. I've not found a need to go above 50psi personally so that one suits my needs well without being too expensive. The lid style is much more secure than the slightly less expensive harbor freight model. Switching it to pressure casting purposes is very very easy.
 
Thanks, Tim ....

You don't have to worry any time soon about losing a pen blank customer !! . I like yours !!

I think that I am an incurable collector of tools ..... and blanks :biggrin:
 
I have the California Air Tools 5 gallon pressure pot which is rated to 90 psi and has worked great. I never considered by the harbor freight similar sized one due to the lack of quality of much of their stuff.
For me, pressure casting absolutely eliminates all the bubbles and helps to force resin into areas where it normally may not flow. Vacuuming the resin to remove bubbles works also but with quick setting resins it can be a challenge to get everything set up in time plus adding colorants and pouring can add more bubbles. I mainly use my vacuum chamber to stabilize wood and to degas Weld-On 40 which is used in acrylic fabrication.
 
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I look at it as insurance. The cost of resin and time make a pressure pot necessary. Especially if your going to do any hybrids or pine cones etc. I went with the HF and its fine for my use. Like any tool use it carefully and double check it before pressurizing.
Before long you will have boxes full of blanks to add to your collection.
 
Great timing for me on the conversation, thanks guys.
Question, is there anything that would preclude using a 5 gallon pressure pot on its side with a support to cast larger pours than just pen blanks?


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I've cast PR using both vacuum and pressure. Vacuum doesn't come close IMO, even when I was sure the resin was thoroughly degassed sometimes I would still get an air pocket. As mentioned, you don't have enough time to use vacuum with Alumilite and if it's hot out, even PR can start to set while degassing.

I just use the regular HF pot and replaced all the fittings with ones I ordered from Amazon, there's a thread here on how to do it. The pot has functioned flawlessly for me, and I have a couple friends that have one and they've never had issues either. I wouldn't mind getting 1 or 2 more - and probably will - so I can have several batches of blanks going at a time. For the price it's a great toy to have if you plan on casting, and absolutely necessary if you'll be using Alumilite.
 
I found this one online ... anybody tried it ?

https://www.artmolds.com/pressure-pot.html

And I found the CAT one mentioned above (which it seems comes from Home Depot)

https://www.homedepot.com/p/California-Air-Tools-5-gal-Pressure-Pot-365B/203526443

But both of these are more expensive than I thought this item should be.

And there is this one for half the price at Harbor Freight (which I don't have ready access to).

https://www.harborfreight.com/2-1-2-half-gallon-pressure-paint-tank-66839.html

And, at Grizzly, there is this one (which they have unkindly priced in Canadian dollars for me !!!! :frown::mad:).

2-1/2 gal. Paint Tank w/ Gauges | Grizzly Industrial

How about this one ... 2.5 gallon from TCP Global ?

https://www.amazon.com/TCP-Global-2...D=41zGVsAMX-L&preST=_SY300_QL70_&dpSrc=detail

Ahah !!! ... Here is a company with a branch not far from me - Acklands Grainger

https://www.acklandsgrainger.com/en...re-Pots/Paint-Sprayers-and-Accessories/c/4806

HOLY COW ! .... I can't believe the prices .... all well North of $1000.00 !!!

I think that Canucks and Yanks speak different dialects on this subject, so I will have to persevere and look for alternative names for the same thing.

Has anyone seen this alarming advice ?

http://www.resinaddict.com/blog/2013/10/safety-announcement-do-not-use-harbor-freight-pressure-pots/
 
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magpens said:
It seems that more and more of our members are learning to cast blanks.

At some point I would like to join in that activity.

I have not looked around seriously for a pressure pot, just asking for suggestions as to what other people use.

One or two of the hardware/tool stores that I frequent sell "paint pots" with a gauge on top, a lid seal, and sturdy clamps. . Is this a pressure pot ?

Another question I have relates to the use of pressure for casting as opposed to vacuum.

My intuition seems to be telling me that vacuum is what you need for casting as opposed to pressure. . Isn't vacuum the way to get bubbles out ?

I do understand the difference between pressure and vacuum and worked with both for many years in my career as an experimental physicist.

In spite of that, as I consider doing my own casting I would intuitively go for vacuum.

Happy to hear what others think.
Click to expand...



If you are casting you want to use a pressure pot (paint pot modified ) it's the best way to get the air bubbles out of your resin and make a good bond with the wood if you are embedding wood the pressure shrinks the bubbles to microscopic size

Now for vacuum that is the best way to stabilize wood as it pulls air out and stabilizing resin in you can stabilize wood with a pressure pot if you have the right setup witch most people don't what I have heard it takes thousands of pounds of psi to achieve that hope this kinda helps if u have any questions feel free to ask I'm not a pro but I know my way around a little


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Mal, I think the dander of using a pressure pot is overblown (pun intended). Be careful and inspect it regularly. I'm no scientist but if it ruptured is it going to explode or simply expel the air? It's not a bomb.
 
PatrickR said:
Mal, I think the danger of using a pressure pot is overblown (pun intended). Be careful and inspect it regularly. I'm no scientist but if it ruptured is it going to explode or simply expel the air? It's not a bomb.
Click to expand...

Patrick ... thank you.

Well, I am not too worried about the danger/risks. I have quite a bit of experience with vessel that are lightly pressurized (50 PSI) and under vacuum.

However, kitchen quality pressure vessels have been known to exlode with quite serious consequences (partly due to the contents, I beleive).
 
Mal there is a Horror Fright within a mile or so of the Grizzly showroom in Bellingham. When you go to get your mail across the line it is only about 20 minutes or so to go to Grizzly or HF for a wallet draining browse.

Princess Auto sell a paint pot equivalent to the one at HF for something around a hundred bucks when on sale.

When a pressure pot lets go it does't just leak air it explodes with enough force to kill or seriously injure you. Used within the makers pressure range they're safe but don't underestimate the energy stored in one if it is compromised.

Have fun but not a blast with your casting. :wink:
 
Hi Curly,

Thank you for your post. I am aware of the HF and Grizzly in B'ham. . I can only speculate on both company's international marketing strategies in placing those stores close to the border. I am uncertain (from my online perambulations) whether either company has a store in the Seattle area.

However, I rarely go across the line. My sister has a rented mailbox in Blaine and she goes every 10 days or so, and that works for me to let her do it as she also has a Nexus pass and she buys her vehicle gas down there and groceries to save some $$.
I pay her well for her courier service !! . I also have to keep my package value within strict limits so that it does not present any problem for her when returning.

Thanks for the warning ... experience doesn't count if the vessel decides to explode, but I would take precautions, such as a strong vented box as a surround.

I have been looking for a pressure vessel of appropriate size at the Princess Auto store in Coquitlam but have not yet found one. I should try Langley.

If you know that PA markets a suitably sized pressure pot and can send me a URL from the PA online store I would appreciate. . Thanks.

I am not sure just how soon I would start casting ... I have so many things on the go ... and I am not sure WHAT I would be casting .... possibly buttons for starters. WoodChuckers in ON used to sell button blanks but not any more as far as I know. . I liked those.

I also have some thought of decorating brass tubes in some way and then casting them in clear resin.

I definitely won't be doing feathers !!!!

I don't suppose your use of "blast" above has any particularly sinister connotations with regard to the contemplated activity !! :biggrin:
 
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Thanks, Pete.

That one is 10 liters ... about 2.5 US gallons. Big enough, do you think ?

Haven't seen those in the local stores but I have only started this consideration.

Which brand of pot do you guys use ?
 
More than big enough.

I got my pot from a dumpster at a paint manufacturer in the late 80's I was doing work for. It had no name plate on it but would have been North American made.
 
I remember those pressure (paint) pots being quite common 60+ years ago. Every commercial and domestic home painter used one.

A lot of them would have been dumpstered ... haven't seen any in use for many years and I guess that's because commercial painting technology has changed a lot.
 
vacuum chamber recomendation

https://www.ebay.com/itm/3-Gallon-S...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

I have used this about 4 times now with cactus juice and it has worked flawlessly. I did have some shipping damage, but lab 1st handled it immediately and at no cost to me to make it right.

Cheapest kit I could find with an actual vacuum pump and I can reliably reach -29.5" Hg with no issue. With the 3CFM pump this can be done in about 5-10 minutes depending on what shape the worthless wood is in.

The out gassing of the material takes MUCH longer ~ 1-2 hours for it to stop bubbling.

I follow this up with 2-3 hours in a toaster oven at ~225 to cure the cactus juice. After trimming/breaking stabilized wood to desired sizes I put into molds and preheat to about 200F. Mix alumilite at ambient with multiple colors and pour into preheated mold. Put in pressure pot at 50psig for about 1-2 hours depending on which alumilite I use. The preheating is huge for a proper cure and no bubbles (at least for me anyway).


Just wanted to share my two cents.

See the two pictures attached as examples of my first and second try.
No bubbles or voids realized when turning.
 

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Mal,

Depending upon what you are planning to do, you can probably get by without a pressure pot for a while and maybe forever. Assuming that you decide to go with urethane resin Alumilite has quite a few videos on its website that are helpful with respect to taming the dreaded bubble.

I have also found this reference to be quite helpful. While it is geared more toward the robotics hobbyist and is at least a couple of years old it is a very good primer on silicone mold making and casting resins along with how they can be modified.

Guerrilla guide to CNC machining, mold making, and resin casting

Bill
 
magpens said:
It seems that more and more of our members are learning to cast blanks.

At some point I would like to join in that activity.

I have not looked around seriously for a pressure pot, just asking for suggestions as to what other people use.

One or two of the hardware/tool stores that I frequent sell "paint pots" with a gauge on top, a lid seal, and sturdy clamps. . Is this a pressure pot ?

Another question I have relates to the use of pressure for casting as opposed to vacuum.

My intuition seems to be telling me that vacuum is what you need for casting as opposed to pressure. . Isn't vacuum the way to get bubbles out ?

I do understand the difference between pressure and vacuum and worked with both for many years in my career as an experimental physicist.

In spite of that, as I consider doing my own casting I would intuitively go for vacuum.

Happy to hear what others think.
Click to expand...
I use the harbor freight paint pot, with little rework it works great.


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