Craftdiggity
Member
Is this something that a fella can buy locally? If so, where?
MEKP
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ldb2000
Member
Home Depot , local Autoparts store , Autobody supply house , even an Auto body shop can give you enough for a gallon of resin if you know someone there .
Craftdiggity
Member
Home Depot? Really? Where would I look?
I see they sell MEK, but is that the same thing?
I see they sell MEK, but is that the same thing?
ldb2000
Member
It's by the glues not by the chemicals . HD sells General purpose resin and the have the tubes of MEKP right near it . Look for the Bondo body filler on the glue isle and the MEKP will be hanging on the peg board , it's in a tube on a cardboard hanging card .
Edit:
You run out ?
Edit:
You run out ?
el_d
Member
I found it at walmart, by the Bondo supplies.
Sylvanite
Member
No. It is the peroxide in Methyl-Ethyl-Ketone-Peroxide (MEKP) that supplies the oxygen which cross-links the styrene monomers in polyester resin. MEK will not work as a hardener.
Regards,
Eric
ldb2000
Member
That was why I said not in the chemicals section , all they have there is MEK which as Eric said "won't work" . You have to look in the glue section .
Craftdiggity
Member
I got the five gallon bucket of resin with a large bottle of MEKP. I am nearly out of the MEKP, but still have close to two gallons of resin. I'm not sure if I have been careless with my mixing ratios or if they didn't send me enough. Also, I have been casting a lot of different materials like coffee beans and rice, etc, and the ratio goes up when you do that if I'm not mistaken.
ldb2000
Member
I use 3 drops per ounce regardless of what I'm casting . I preheat my resin and it starts to gel within 5 minutes , a little longer for a few pigments .
Brooks803
Member
Chris I have an unopened bottle from uscomposites if you need it. It's the size you get with a 5gallon bucket.
Craftdiggity
Member
3 drops??? The instruction I have in front of me say 10 drops per ounce.
Craftdiggity
Member
Thanks, Jonathan. Let me see if I can find it at HD. If not, I might take you up on that.
rjwolfe3
Member
You made need to experiment. I use 4 drops myself.
Brooks803
Member
No problem...I think you can also find it at hobby lobby or michaels where the castin craft is. btw the bottle isn't very old either and its been kept in a cabinet inside the house since I got it. I use 3-4 drops per oz myself.
ldb2000
Member
Yep , 10 drops is what they call for and after experimenting with a number of gallons I have got it down to 3 drops per ounce . During the winter when the temp in my shop is around 50 degrees I use a little more (5 to 7 drops) .
Technically you don't need any MEKP to cure the resin but you have to heat it to cause the reaction . The MEKP just causes the reaction to kick off .
If you can't find the MEKP in the HD by you just go to any NAPA autoparts or Autozone and buy it there . They all carry it , it's the same stuff used for doing fiberglass body repairs (not the cream hardener for body putty , the clear liquid hardener for fiberglass resin) , it's about $3 to $5 for a tube .
Sylvanite
Member
Yes and no. Although polyester resin will harden without MEKP, it will not form the same chyrstalline structure. The oxygen from MEKP links the polyester polymer chains together forming a much stronger and harder solid. MEKP is not an accelerator. Many PR formulations (including Silmar 41) come "pre-promoted" with cobalt napthanate. That is the accelerator (or in industy terms, the "promoter"). MEKP reacts with the cobalt naphtanate, generating heat which helps drive the polymerization (turning styrene into polyester) and the peroxide cross-links the polymers for strength. Thus, MEKP is a "hardener". Other promoters and hardeners also exist.
Not enough MEKP will yield a cast that is slow to set and soft when cured. Too much will result in a rapid cure that is hard but brittle.
Regards,
Eric
LandfillLumber
Member
I use .9% of MEKP by volume and have found it to be a nice mix between hard enough for a nice shine and not to brittle to work.Good Luck,Victor
Craftdiggity
Member
Found it @ HD. Thanks fellas. I'll be experimenting with my ratios now, I suppose.
KDM
Member
:biggrin:Seems unlikely. It would be highly explosive.
Which brings me onto the conversation about ratios. Mecause raw MEKP is hi-ex, the suppliers, vendors, etc, dilute it before transport. I'm not at all confident that they're very particular with their mixing ratio so long as they get it to a point where it's declassified.
I've kept a log of each batch I bought and always mix by volume. The gelling time is never the same twice. I really don't think it's a science. All other variables are the same: temperature, colour quantities, etc.
bruce119
Member
I have a bunch of that stuff around. The amount they give you say for a 5 gal. is about 10xs what I use. So I got a bunch of open bottles lying around. When ever I get a new 5 gal. of resin I move onto the new MEKP. Anybody need some just ask. But it would probably be cheaper to buy at the craft shop.
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PenMan1
Member
If you have a boat dealer or Corvette body shop near you the will likely give you all the MEPK you can use. We used to give it away at the boat dealership.
You will need to experiment with the amount of mepk you need to use. Temp, humidity, thickness of the pour, and yes, even elevation above sea level will all effect how much catalyst is needed.
In South Georgia (very hot, extremely humid and only 300 to 400 Ft above sea level) five drops per ounce works nicely this time of year. In the winter 6-7 drops per ounce works better.
I have never known of a place where 10 drops per ounce is needed.
You will need to experiment with the amount of mepk you need to use. Temp, humidity, thickness of the pour, and yes, even elevation above sea level will all effect how much catalyst is needed.
In South Georgia (very hot, extremely humid and only 300 to 400 Ft above sea level) five drops per ounce works nicely this time of year. In the winter 6-7 drops per ounce works better.
I have never known of a place where 10 drops per ounce is needed.
atomic ray
Member
Correct! MEK is a solvent; Butanone. It has many uses, mostly with cleaning and changing states like with film.
As for the amount of MEKP to use, Eric is right on the money.
Resin will harden without the MEKP but that does not mean that it will cure.
Curing comes with a stable stacking of the resin into balanced crystals which comes from thermal reaction. Consistent heat, either eno or exo, will initiate the process but the non-industrial fabricator should only rely upon the chemical catalyzing action of MEKP.
A small amount, even a drop, will engage the process but the ratio to create a stable balance is a complex formula that considers time, state, humidity, ambient temperature, fillers, resin age (pre crystal formation), and the chemical composition of the resin itself.
Too little will give you a slow cure. Too slow will push the uncured resin forward or outward, thus you get the sticky or soft surface...this is an easy fix with casting wax, just a drop or two.
Too much will excite the process but will also create hot pockets of cured material within the slower curing sections, creating spiderwebs within the structure...resulting in a brittle structure.
Another consideration is the amount of resin. The more resin the hotter the core as the chemical heat stacks creating a heat source that that can exceed the recommended safety factors...I deal with gallons at a time while working with kevlar and large boat hulls.
But for small batches the best process is the one that works.
My drill sergeant at boot camp; Paris Island 1983 SSGT Skelly, told me (us) that there are two ways to do anything...your way and the right way.
In this case the right way is your way...you must try the line as it were.
If you have used 10 drops and are happy with the results and you fellow casters are saying 3-4 drops...perhaps consider the happy and reasonable option...try 5 drops.
It is a nice even number and saves you half the MEKP...if it works for you, where you are, the way you work with the resin.
Good luck with your projects.
Raymond
:bananen_smilies046:
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bitshird
Member
BUT if you are doing "ribbon casting" which the resin will only be about .030 to .050 thick then you need about 30 drops per OZ, the amount used will vary by the thickness of the cast, 1 inch molds 4 drops per OZ7/8 and 3/4 3 drops per OZ, bottle stoppers in a 1-1/2 inch tube and 2 inches tall 2 drops work fine, real thin like for ribbon casting 30 to 40 drops per OZ most pen related 3 to 4 drops work very well.
KDM
Member
Yeah, me too, so I wonder if Craftdiggity's castings are really brittle.
Not me. I'm partway through PR bucket number 3 and jus about done MEKP bottle number 1!
KDM
Member
PTownSubbie
Member
Ribbons are normally soft to allow manipulation, at least that is how I try to make them.... Won't 30 dp/oz make it very brittle? I will have to give this a try and see what happens. When you make the ribbons, do you roll them or just break it up and put it in your next cast?
Is this potentially why some of my casts end up tacky on top and others don't? A little time outside in the sun cures this no problem but could it mean that it is not fully cured prior to the sun bathing? I am going to have to start paying attention to this closer and put this in my log also.
What is this casting wax and what does it prevent??
bruce119
Member
Mine are always tacky on top after 12 hrs and always have been. Unless I put a ton of MEKP in and then they are noticeably brittle. The Tacky top layer is easily fixed with about 3-4 hours out side in the warm air. If it's raining I put them in the garage it's hotter then heck out there. Now in the winter on that rare cold day I mite put them under a 60 watt light bulb. I have had complements on how nice my blanks turn. I do 3-4 drops per once and leave them set for 12 hrs. That is in a A.C. shop at 78. I experimented with more MEKP what is recommended and it was like turning glass you had to be real careful or it would chip real easy.
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ldb2000
Member
The tackiness is a design feature of polyester resin , it allows the next layer of resin to bond fully to the previous castings . Yes it will bond when fully cured but the bond will be better when tacky . A surfacing agent (styrene wax solution) gives a finished surface to the resin when a finished casting is not going to be finished any further . You can buy surfacing agent at any fiberglass supply shop , it is an additive to the resin used to make many fiberglass products with a finished surface , like surf boards and car accessories like spoilers . The resin with the agent already mixed in (as well as pigment in some cases) is known as Gel Coat .
atomic ray
Member
bruce119
Member
I think we here with the pens and what we are doing embedding objects, making sure it has good turnable properties is all experimental. Resin wasn't made for what we are doing with it we are making it work for us. For the most part boats & surf boards are the main use of resin. But all this info. helps us to figure out how to make the resin work for us.
All good info.
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All good info.
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Craftdiggity
Member
bruce119
Member
Craftdiggity
Member
Nothing to clear up, Bruce. I didn't see anything offensive anyway, just a question. But I appreciate the CYA.:wink:
KDM
Member
The heat can make them cure faster, making them brittle, but I'm surprised it had that much effect. Are the pinholes due to the tool catching in the brittle material, or are they actuall air bubbles? It's easy to introduce air bubbles at the gel stage.
If you make a block, you can alwasy keep one, in case you get a heavy-handed moany customer. Then yuo can turn the one you kept just to satisfy yourself.
DurocShark
Member
I've always been happy with just enough MEKP to kick off the reaction, then post curing in the toaster oven.
All this other stuff seems like too much work. heh
All this other stuff seems like too much work. heh