Pr casting ?

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J

jack barnes

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Joined
Aug 5, 2005
Messages
371
Location
Springfield, Ma.
Ok temp. this weekend is supposed to be in the 80s.
After my last try I have some left over pr. How much MEKP pre ounce do you suggest. I'm going to set pot pressure at 45psi and leave for 24 hours.

Jack
 
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Seems like 45-50 drops should be ok for that amount.. you could do with less
if it will be kept warm. That's my guess
 
jack barnes said:
Thanks, By the way Charlie I'll bring you another roll of tape to the next meeting on the 17th.

Jack
Click to expand...

WOOHOOOO!!!!! I'm using that tape all over the place. I use it for making
molds .. the masters tend to float in silicone, so the tape holds the parts
down when I pour. Good deal!! :biggrin:
 
I would figure the oz.'s , which I'm guessing should be approx. 7. I think 45-50 might be too much for that size of a casting. Just my $.02
 
depends on the brand of PR. CC would take 4-6 drops per ounce at the thickness. silmar 41 seems to ask for a lot more, 10 drops per ounce. at 80 degrees and 24 hrs in the pot. I personally would not use more that 6 drops per ounce for a 3/4 cast. all the brands I have seen will have the proper ratio printed on the back.
 
Let's see .. 6 x 5 x .75 is 22.5 cu. inches at around .55 ounces per cubic inch..
That's about a 12 ounce pour, give or take. so 50 drops would be around 4 drops
per ounce.

Don't forget, the MEKP just kicks off the reaction. PR will harden even without it, it
just takes more heat and more time to do it.
 
Sorry Charlie,

you are probably right, I'm used to casting round blanks. Haven't cast squares or slabs in a while. They do require more resin to yeild the same blank. That is why I started casting the rounds.
 
why 24 hours in the pressure tank? Is that amount of time arbitrary? Polyester resin should be cured in just a few hours. I routinely take my casts out of the pressure tank after 5 hours and I use 3 drops of MEKP per ounce. The left over PR in the pouring jar is often hard after just an hour. Once the resin has hardened the pressure tank is no longer serving any purpose. So, I'm just wondering???
Do a good turn daily!
Don
 
Don, I can't get close to those results in Colorado in winter with Castin Craft. For me, the cc sets in about 2 hours, but stays warm for much longer.

Just demonstrating the wild variables that mean a different experience for each user.

BTW, I use way more MEKP than recommended when temps are below 70.
 
Have you tried heating the resin in a hot water bath prior to adding the catalyst? The ultrasonic cleaner I use has a heater and warming the resin first is working great for me...and for Roy (Oklahoman). The warmed resin thins out and air bubbles can rise to the surface much easier. Be careful how you heat it. PR has a flash point of 88 degrees.
Do a good turn daily!
Don


Do a good turn daily!
DurocShark said:
Don, I can't get close to those results in Colorado in winter with Castin Craft. For me, the cc sets in about 2 hours, but stays warm for much longer.

Just demonstrating the wild variables that mean a different experience for each user.

BTW, I use way more MEKP than recommended when temps are below 70.
Click to expand...
 
mostangrypirate said:
well.....the weekend is almost gone. what have you made?
Click to expand...

..a mess of my shop.

I have spent the last few hours trying to clean, but it just gets worse
the further in I get. On a good note, I've found things that haven't seen
the light of day in a long time. (I think I found the Lindburgh baby)

Finally getting around to hooking up dust collection ports that have been
sitting on a shelf waiting for me to get time ..
 
NewLondon88 said:
..a mess of my shop.

I have spent the last few hours trying to clean, but it just gets worse
the further in I get. On a good note, I've found things that haven't seen
the light of day in a long time. (I think I found the Lindburgh baby)

Finally getting around to hooking up dust collection ports that have been
sitting on a shelf waiting for me to get time ..
Click to expand...


Made me laugh because I just did that a couple days ago. I was putting my turning stuff away so I can break out my scrollsawing stuff. I found all kinds of blanks, bushings I thought I lost or got sucked up in the dust collector, and a bunch of book markers I started making last Nov. which I totally forgot about. I can actually see the table top on my work table.:biggrin:
 
LOL .. I just found three sets of bushings I had misplaced. Two weeks ago I
went to Woodcraft and got new ones.

On a good note, I've got a few hundred more blanks than I thought, and
three sheets of 3/8 plywood I couldn't find (hidden behind a tarp hanging
on the wall) and I now have 4 socket sets and 17 measuring tapes..
 
I'm afraid to clean up the shop. If I did, I wouldn't be able to find anything. Kind of like it is now...:beat-up:
 
Here is how the casting went. First of all I intended to cast on sat, but the wife put a stop to that. She had a surprise birthday party for me. (62). Got a lot of good stuff. 32 pack of Pearl Ex
1. Virgil 24hr in pot was jest a number in my head, after reading your post took it out after 6hr and it was setup, looks good will see tomorrow
2. Used plastic cups from dollar store, big mistake, soon as I add MEKP they melted
3. cast out side forgot to level table. level not bad but one side about 5/8" thick the other about 7/8" not going to be problem.

Jack
 
jack barnes said:
Here is how the casting went. First of all I intended to cast on sat, but the wife put a stop to that. She had a surprise birthday party for me. (62). Got a lot of good stuff. 32 pack of Pearl Ex
1. Virgil 24hr in pot was jest a number in my head, after reading your post took it out after 6hr and it was setup, looks good will see tomorrow
2. Used plastic cups from dollar store, big mistake, soon as I add MEKP they melted
3. cast out side forgot to level table. level not bad but one side about 5/8" thick the other about 7/8" not going to be problem.

Jack
Click to expand...


Jack~~~~~ Happy Birthday

Glad things worked out for you and the pearlX is a great gift.
 
Been reading about all the drops per ounce here, makes my head spin!

I used to count drops as well, but not for long, too much time and too prone to mistakes, fancy counting 40-50 drops.

I'm sure the little plastic pipettes that I use are available in the US? They measure up to 3ml (sorry, we are metric!) and I use 1ml per 100 grams (bit under 4 ozs).

Quick easy and not prone to miscounts, interruptions and the like.

The little pipettes cost next to nothing, I bought 10 to start with and am still using my first one.

http://www.barnesonline.com.au/product.asp?strProdFamily=Dispensers
 
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