pressure pot

Signed-In Members Don't See This Ad
Signed-In Members Don't See This Ad
Google This:

Just This and That: DIY Pressure Pot Conversion: Part I

A 3 part article from a blog about casting silicone models.

Very extensive.

Good luck
 
waste wood blanks with Silmar 41 ??

I have cast quite a few waste wood blanks using off the shelf fiberglass resin and have really never had any problems other than the color gets muted because of the tan color of the resin. I recently bought two gallons of Silmar 41 and I have cast some buckeye burl, cocobolo, elm burl, cherry burl, and some maple burl. With the buckeye and the cocobolo I had issues. I am using 7 drops of MEKL per ounce and I am casting in HDPE molds that I made. With the cocobolo the blanks did not fully cure out in some spots mostly on the bottom. With the buckeye the resin seemed to want to pull away from wood. The rest seemed to cast ok. Is this a known problem with woods like buckeye and oily woods like cocobolo? I have quite a bit of coco and buckeye to cast so any help or advice would be greatly appreciated. Thank you in advance.
 
woodwzrd said:
I have cast quite a few waste wood blanks using off the shelf fiberglass resin and have really never had any problems other than the color gets muted because of the tan color of the resin. I recently bought two gallons of Silmar 41 and I have cast some buckeye burl, cocobolo, elm burl, cherry burl, and some maple burl. With the buckeye and the cocobolo I had issues. I am using 7 drops of MEKL per ounce and I am casting in HDPE molds that I made. With the cocobolo the blanks did not fully cure out in some spots mostly on the bottom. With the buckeye the resin seemed to want to pull away from wood. The rest seemed to cast ok. Is this a known problem with woods like buckeye and oily woods like cocobolo? I have quite a bit of coco and buckeye to cast so any help or advice would be greatly appreciated. Thank you in advance.
Click to expand...
Did you use pressure? Even if you didn't, I'm not sure that would have helped. Silmar 41 shrinks a lot, so I think there will always be the chance of it pulling away from the wood. Plus, 7 drops might be a little too much MEKP. But maybe not. The thinner the resin, the more MEKP it needs. I use 4 drops with regular casting of blanks. Also, did you check the moisture content of the buckeye? If it wasn't dry, that may have caused you some issues. I can see cocobolo being a problem because of how oily it is.

I know this doesn't help much, but when I cast wood, I use alumilite. Mostly due to less shrinking. But I've never cast cocobolo with any resin.
 
BSea said:
woodwzrd said:
I have cast quite a few waste wood blanks using off the shelf fiberglass resin and have really never had any problems other than the color gets muted because of the tan color of the resin. I recently bought two gallons of Silmar 41 and I have cast some buckeye burl, cocobolo, elm burl, cherry burl, and some maple burl. With the buckeye and the cocobolo I had issues. I am using 7 drops of MEKL per ounce and I am casting in HDPE molds that I made. With the cocobolo the blanks did not fully cure out in some spots mostly on the bottom. With the buckeye the resin seemed to want to pull away from wood. The rest seemed to cast ok. Is this a known problem with woods like buckeye and oily woods like cocobolo? I have quite a bit of coco and buckeye to cast so any help or advice would be greatly appreciated. Thank you in advance.
Click to expand...
Did you use pressure? Even if you didn't, I'm not sure that would have helped. Silmar 41 shrinks a lot, so I think there will always be the chance of it pulling away from the wood. Plus, 7 drops might be a little too much MEKP. But maybe not. The thinner the resin, the more MEKP it needs. I use 4 drops with regular casting of blanks. Also, did you check the moisture content of the buckeye? If it wasn't dry, that may have caused you some issues. I can see cocobolo being a problem because of how oily it is.

I know this doesn't help much, but when I cast wood, I use alumilite. Mostly due to less shrinking. But I've never cast cocobolo with any resin.
Click to expand...

Thanks for the reply BSea

I did use pressure. I forgot to add that part. I cast everything under 80#. The buckeye was bone dry as was the coco.

My first pour was with 4 drops of MEKP and I ended up throwing the blanks away because they never fully set in places after one full week. I set them in the sun for two days and that didn't help either. I set the mold aside after I took the blanks out and there is still some gooey un-cured resin in the mold and that pour was two weeks ago.

I have had great luck with alumilite for waste wood but prefer the longer open time with the Silmar 41.
 
dscott, I apologize for hijacking your thread. I intended to start a new thread with my question and accidentally hit the reply to you thread instead. I am sorry.
 
The tutorial here creates a hybrid pressure/vacuum pot. If you want just a pressure pot, you can skip all the vacuum-related portions of that tutorial. It will simplify things quite a bit.

Just make sure to cap off the unused side....

I went with a Binks pot since they're tested to a higher pressure level. The paint pickup tube inside was threaded into the lid...trivial to remove it (vs. having to cut off the tube with the Harbor Freight pot if I recall the tutorial correctly).
 
FYI, I just modified a Harbor Freight pressure pot. The paint pickup tube is loosely threaded (I understand they used to be different).
My biggest issue was sealing up the threaded hole for the paint pickup. I had a hard time finding a plug that would fit. I found one, used teflon tape, and it still leaked. I finally filled the hole underneath the lid with JB Weld. Seems to be working now. It holds 40lbs for several hours, although it does slowly leak out eventually. Not a big deal.
Steve
 
sdivot said:
FYI, I just modified a Harbor Freight pressure pot. The paint pickup tube is loosely threaded (I understand they used to be different).
My biggest issue was sealing up the threaded hole for the paint pickup. I had a hard time finding a plug that would fit. I found one, used teflon tape, and it still leaked. I finally filled the hole underneath the lid with JB Weld. Seems to be working now. It holds 40lbs for several hours, although it does slowly leak out eventually. Not a big deal.
Steve
Click to expand...

It's been years since I built my pot so it's kind of hard to picture it in my head, but it seems that I used a standard fitting in that hole. I know that I didn't have to take any extreme measures to plug it.

I'll try to remember to take a look at what I came up with the next time that I am at the shop.
 
Steve, thanks for offering to let us know what you used to plug that paint pickup tube port. I just bought the HF pressure pot, and in mine that tube is also loosely threaded into the lid. I'm just starting the process of setting it up for casting, and would very much appreciate knowing what you found to work and used.

Thanks.

Hugh
 
hughdrbf said:
Steve, thanks for offering to let us know what you used to plug that paint pickup tube port. I just bought the HF pressure pot, and in mine that tube is also loosely threaded into the lid. I'm just starting the process of setting it up for casting, and would very much appreciate knowing what you found to work and used.

Thanks.

Hugh
Click to expand...
Thanks for the post, because I had completely forgotten about the offer. I'll wander down to the shop in a few minutes to take a look.
 
Last edited:
I took a look. As it turns out, I didn't plug up that hole. I didn't even remove the fittings that were there. I unscrewed the paint tube and screwed in standard copper fittings. In my pot, that side connects to my air line and the other side has my pressure and vacuum gauges, although I haven't used my pot for vacuum since I bought one of MM's chambers some time ago.

Pics to follow as soon as I can figure out how to get them from my phone to the forum.
 
Lousy sideways pic of the top of the pot:

1_image.jpg
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom