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jtdesigns

jtdesigns

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Okay, so I am fairly comfortable and experienced with PR (Sil-41) and I was doing a mixed media cast with wood chips (bloodwood, ebony, maple) and some brass shavings. I mixed all my ingredients with uncatalyzed resin to ensure I had good mixing without it setting up to fast. I had approx. 3 oz of resin and added 9 drops of MEKP. This was 7 days ago and the mixture is still a gloppy mess with none of it hardening. Here are the facts:

Resin is one month old
MEKP was stored without red cap (can it go bad?)
The mixing of media, resin, and catalyst was thorough

What in the he$% happened? Never had any problem before.
 
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I can't really say much about what might have happened. But see if setting it in sunlight causes it to set. I know at least some resins set from UV light.
 
Jeff, I have not mixed S41 and ebony. But I know that PR does not always play nice with other oily woods (Like cocobolo - DAMHIKT :rolleyes: :biggrin:).
 
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Jeff, the 3 drops per ounce is a good rule IF there is enough thickness of the resin. See if I can explain it another way, If you put all the stuff in with the uncured resin, then put it in a mold the resin may only be an 1/8th of an inch in places, the thicker (in depth or mass) the resin is, the less catalyst is needed, it's like if you try and cast rice or some spices or dried peas, you have to bump up the amount of MEKP because there isn't enough mass of resin, to create the heat necessary to cure. The casting may have been 3/4 thick but how much of the volume was resin?,
 
bitshird said:
Jeff, the 3 drops per ounce is a good rule IF there is enough thickness of the resin. See if I can explain it another way, If you put all the stuff in with the uncured resin, then put it in a mold the resin may only be an 1/8th of an inch in places, the thicker (in depth or mass) the resin is, the less catalyst is needed, it's like if you try and cast rice or some spices or dried peas, you have to bump up the amount of MEKP because there isn't enough mass of resin, to create the heat necessary to cure. The casting may have been 3/4 thick but how much of the volume was resin?,
Click to expand...

Sounds reasonable, I might try it with more catalyst. Is there a shelf life with MEKP though?
 
jtdesigns said:
Sounds reasonable, I might try it with more catalyst. Is there a shelf life with MEKP though?
Click to expand...

Not sure if I remember this correctly but I believe Gary_Max had said once that MEKP can go bad but I think it takes >6 mo or so...

I may be wacked out of my rocker though....
 
MEKp is a peroxide and as peroxides like to do, they oxidise, and break down. Keep it tightly sealed, dark and cool, and you should easily get 6months or more. If not then buy small quantities frequently.
 
I love saying methyl ethyl keytone peroxide, but I'm not going to mention it. Yes, MEKP can break down. It's an oxidant, so it will cause anything with which it comes in contaact to oxidise. Moisture in the air being a good favourite.

Would there be any merit in mixing the catalyst with the PR before adding the woodchips? I imagine if the catalyst is absorbed into the woodchips (it's nice and thin where the PR is thick and gloopy), then it won't be catalysing anything.
 
well, remember that PR resin will set without any MEPK if heated enough. If a day in the sun didn't do it, then try a half hour in the toaster oven at 200. If that don't do it either the pr itself is bad or something else is is killing the reaction. Try a small cast of solid resin with double the mepk and see if it will set up. That will tell you if the pr itself is ok.

James
 
this happened to me one time when I cast a loofa. I used too much black. There might have been something on the loofa? It took weeks to set up. Hey! I still have that I guess I'll have to turn it!
Alice

jtdesigns said:
Okay, so I am fairly comfortable and experienced with PR (Sil-41) and I was doing a mixed media cast with wood chips (bloodwood, ebony, maple) and some brass shavings. I mixed all my ingredients with uncatalyzed resin to ensure I had good mixing without it setting up to fast. I had approx. 3 oz of resin and added 9 drops of MEKP. This was 7 days ago and the mixture is still a gloppy mess with none of it hardening. Here are the facts:

Resin is one month old
MEKP was stored without red cap (can it go bad?)
The mixing of media, resin, and catalyst was thorough

What in the he$% happened? Never had any problem before.
Click to expand...
 
jtdesigns said:
Sounds reasonable, I might try it with more catalyst. Is there a shelf life with MEKP though?
Click to expand...

I'm using some that is nearly or just over a year old, and it's working at three drops per ounce doing snake skins in a resin saver mold, it took about 36 to 48 hours to cure, but it did. I'll post pics of the pen later tonight.
 
MEKP does not normally go bad, but it can be contaminated and it can be polluted...water, other air born chemicals (bleach, detergents, etc.), salts, and other related unintended additives.

That said, I have used a 5 gallon can over the period of a year without issue.

But as far as goopy curing...that is a fairly common issue with poly resins that are not mixed completely with the catalyst.

By your description I would say your intention was good...to create a skin and thus reduce the potential for air bubbles/pockets...but I would have removed the materials/strained them, then add them to the molds, then mix your resin/catalyst, pour, and apply your vacuum if you have one.

I am new on the board but I have been dealing with resin and glass projects since '83.

Goopy curing usually only has one culprit...a breakdown of the catalyzing process. Now that said it could be from poor mixing, old resin (resin will start to crystallize and partially solidify creating grains), compromised resin (salts, water, oil, etc.), and contaminated mixing devices (old sticks, used cups, and other elements that can bring curing resin to the mix).

Best thing to do at this point IMO is to remove the goopy piece, let it set up, and then see what you have to work with.

Did you add any wax to your resin? A small amount, a few drops per quart...fairly close or a bit more than the amount of catalyst...this allows for a seal and is a must in an area with high humidity. Usually bound with a styrene base.

You could use 05-13% styrene to thin your resin and change the viscosity if you are worried about air bubbles/voids...the thinner mix will let the bubbles rise easier.

But usually with a goopy mess...it is better to cut your losses...put it away and come back in a month, it will eventually cure, and then deal with it.

Out of sight out of mind.

PS
Make a small batch of the same resin and MEKP, leave it in the cup and see if it sets up. If it does then it is not your resin.
 
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