PR won't harden

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C

Charles

Member
Joined
Sep 11, 2005
Messages
357
Location
Spring, Texas, USA.
Help, In my last post I needed help in coloring the PR. Suggestions were to use enamel paint. Got both black and yellow paint from michaels. New can of PR and MEKP. Mixed alittle over 1oz with 8 oz of PR to get the right color. Added MEKP and stirred... and Stirred... and Stirred. never would harden. Added more MEKP. ...nothing. Finally added 2.5x's the amount of MEKP. never harded. Went to black container. I had used 1/2 oz to 7oz of PR and added small scoop of Mica Powder. Added MEKP and it never hardened. Added 1/2 bottle of MEKP and never hardened. Sooooo. Tell me what is going on. I have got to get a 1x1x5.5" yellow and Black swirl blank made for a customer. Please shed some light on this. I never have any problems casting snake or other items in clear. But coloring this stuff is driving me nuts. Now I have to scrape clean the mold and throww out 16oz of PR. Also used light coating of cooking oil as mold release. This should not be the prob. since the black would not get hard even in the plastic cup. All comments welcome. Please get me through this.
 
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Charles, from my great experience with PR (one casting just now), I colored mine with artist oil paint thinned with very small amount of pure mineral spirits (paint thinner). It was poured into my home made mold and heated in my wood dryer for an hour. I just turned one of them. Looks like crap but it did get hard. When I turned it, it was just a bit chippy, but it did get hard and polish up pretty nice. I was afraid that the color and, or thinner would cause problems. What temp are you trying to cure with? From what I can find out, below 65F, never 75 to 65F very slow. Above 100, below 150 quick. I wish I had better info for you. It may be the paint has something in it that slows the hardner a lot.
Charles
 
from what it sounds like to me... is that you used too much colour... the max you should use... (and ANYONE correct me if I am wrong) is 10% of colour to your resin.

I work on this.. resin... then 2% hardner and up to 10% colour. I really use half that in colour because the paste seems to work...

good luck and let me know.. but I really think your using too much colour by the sounds of it...
 
A couple things to keep in mind.

Additives you should really try and use what is made for resins such as dies and mica powders. Sounds like you where tiring to achieve an opaque color. The more stuff you put in PR the longer the set hence the need for more MEKP. Sounds like you used 1 oz of paint to 8 oz of PR WAY too much the color should be added in drops they the PR suppliers have dies transparent and opaque for this purpose. Micas are great but are a bit transparent you get a nice luster and glitter but should paint the inside of the drilled hole.

Also temperature is very important. You did not mention any room temps. I have trouble this time of year even here in Florida. Your room ambient temp. needs to be ideally around 75 or more. If it gets below 68-65 it will never cure.

Now PR cures with heat. Heat is generated chemically by the MEKP don't throw your cast away in time and little warmer temps it will cure. Now you can put it in an oven at about 150-175 for about 2-3 hours then let it cool in the oven another several hours and that should cure it. Now only problem with the oven cure and high temps it will make the blank more brittle and harder to turn not imposable just harder.

Hope I helped these are just my opinions and experiences. No one has the correct answer as every situation is different.

Bruce
 
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Way too much paint. That is why I don't use paint.
Paint is nothing more than pigments in a carrier medium... why add the medium to the cast? Use pigments only and eliminate the other additives.
 
DozerMite said:
Way too much paint. That is why I don't use paint.
Paint is nothing more than pigments in a carrier medium... why add the medium to the cast? Use pigments only and eliminate the other additives.
Click to expand...

Exactly and those who use paint just use the pigment. Now take testers when it sits for a time the pigment settles you can see the medium on top therefore the need to stir before using. Now if your going to use something like this DO NOT STIR pore off the top oily medium and just the the pigment below. Remember this is concentrated only use just enough to get color. If you need an opaque you will have to use a die from one of the PR suppliers be sure and get opaque.
 
Thanks, If you look at my last post on how to color, someone told me enamel paint at 1/2 oz to 8oz of PR. This is what I tried but?? I also tried the HF powder coat pigments but there yellow was actually orange. I need to make this opaque as it will be turned into a rod seat for a custom fishing rod, made by a local rod maker. It will be bored out by the maker to a rather large diameter for the rod blank. So it must be opaque. When you mention the PR companies for colors are you refering to Artstuf? I am not aware of others/ Suggestions please. BTW room temp here in texas was about 70. Has anybody used a hair drier to increase the curing time prior to mixing the two colors? Also the mica powder was added to the black to lend some sparkle to the blank. Amy other suggestions as to a deep yellow color, opaque. Thanks for all your help. And Bruce, love the Franklin money blanks I got from you. Also wooried about putting mold in oven due to ut us a silicone mold.
 
The silicone mold should be fine in the oven. Put a piece of wood under the mold so their is no contact of the mold with metal. Depending on the silicone used, it should handle 200-375 degrees. I would set the mold on a piece of wood and set it in the oven on the lowest temperature and only for about 8 minutes. You don't want to over heat the resin as that can make it brittle and possibly even crack before you even get it out of the mold. Give it 8 minutes, pull it out and let it cool for 30 minutes..then poke it with a pin. If it's not hard, but it is gelling up, put it back in the oven for 8 more minutes and that should be enough to stimulate it to cure up on it's own.
 
Charles said:
Thanks, If you look at my last post on how to color, someone told me enamel paint at 1/2 oz to 8oz of PR. This is what I tried but?? I also tried the HF powder coat pigments but there yellow was actually orange. I need to make this opaque as it will be turned into a rod seat for a custom fishing rod, made by a local rod maker. It will be bored out by the maker to a rather large diameter for the rod blank. So it must be opaque. When you mention the PR companies for colors are you refering to Artstuf? I am not aware of others/ Suggestions please. BTW room temp here in texas was about 70. Has anybody used a hair drier to increase the curing time prior to mixing the two colors? Also the mica powder was added to the black to lend some sparkle to the blank. Amy other suggestions as to a deep yellow color, opaque. Thanks for all your help. And Bruce, love the Franklin money blanks I got from you. Also wooried about putting mold in oven due to ut us a silicone mold.
Click to expand...

If you want sparkle, and that shifting appearence as the angle changes, I would use yellow mica powder. When the blank is drilled, paint the inside with yellow testors or a spray paint. Of you paint the drilled hole, then the opacity doesnt really matter.
 
Powdercoat is not a pigment and is hydrophobic. It doesn't make a good colorant for resins, use dry pigments or the manufacturers dyes.







This is one of the yellows I used to cast.



zz2.jpg
 
I used the transparent yellow dye from US Composites and a touch of white mica powder to make the blank opaque for this pen . The blank has some nice depth to it . The mica powder made the yellow tint very opaque and I didn't have to paint the inside of the hole or the tubes .



The yellow color is brighter in person and there is a swirl from the mica powder . I called it Lemon Chiffon because that is what it reminded me of .
 
Charles said:
Help, In my last post I needed help in coloring the PR. Suggestions were to use enamel paint. Got both black and yellow paint from michaels. New can of PR and MEKP. Mixed alittle over 1oz with 8 oz of PR to get the right color. Added MEKP and stirred... and Stirred... and Stirred. never would harden. Added more MEKP. ...nothing. Finally added 2.5x's the amount of MEKP. never harded. Went to black container. I had used 1/2 oz to 7oz of PR and added small scoop of Mica Powder. Added MEKP and it never hardened. Added 1/2 bottle of MEKP and never hardened. Sooooo. Tell me what is going on. I have got to get a 1x1x5.5" yellow and Black swirl blank made for a customer. Please shed some light on this. I never have any problems casting snake or other items in clear. But coloring this stuff is driving me nuts. Now I have to scrape clean the mold and throww out 16oz of PR. Also used light coating of cooking oil as mold release. This should not be the prob. since the black would not get hard even in the plastic cup. All comments welcome. Please get me through this.
Click to expand...

I believe part of your problem is adding the color before the hardener. I tried casting a blank using turning shavings from corian to add some color and effect, i added the shavings before the hardener, and it never hardened at all.

Maybe someone else can add to that....
 
Polarys425 said:
I believe part of your problem is adding the color before the hardener. I tried casting a blank using turning shavings from corian to add some color and effect, i added the shavings before the hardener, and it never hardened at all.

Maybe someone else can add to that....
Click to expand...

I have to say I disagree.

I would always add the color die or pigment to the resin BEFORE adding the MEKP. A few reasons for this you have more time to mix the the pigment in and let it sit to let the air escape. Then slowly mix in the MEKP trying not to introduce air bubbles. Heating the resin (before MEKP) helps a lot not too much just about 100 deg. The last thing I do in any mix is add the MEKP last. Now in your case with the shavings I would consider the shavings the media. I would mix the color in the resin before MEKP then mix in the MEKP pore into the mold then stir in the corian shavings.

Most problem with resins, no the 2 main reasons for resins not setting is to much additive (die, paint, pigment, whatever) and even more important low room temperature. A sticky surface with a cured cast is normal to harden the surface put the cast in a warm place preferably outside in the warm sun but this time of year in most parts not is not available. Try a warm spot like around a heat duct that has some air flow a couple of hours.

Isn't playing with resin fun :biggrin:
 
Where did your MEKP come from? If not a normal supplier with good turnover, it could be bad..... MEKP is good for usually 6 months depending on conditions.

If your MEKP is bad, it will never harden and that is what you said is happening even after adding a ton of MEKP.

Another thought....what color are you mixing. Certain colors, red in particular, don't harden very readily. Black usually hardens faster.....

Just some thoughts.

Try a small clear cast with the MEKP. That will tell you if it is the additive or the amount of color you are adding.
 
PTownSubbie said:
Where did your MEKP come from? If not a normal supplier with good turnover, it could be bad..... MEKP is good for usually 6 months depending on conditions.

If your MEKP is bad, it will never harden and that is what you said is happening even after adding a ton of MEKP.

Another thought....what color are you mixing. Certain colors, red in particular, don't harden very readily. Black usually hardens faster.....

Just some thoughts.

Try a small clear cast with the MEKP. That will tell you if it is the additive or the amount of color you are adding.
Click to expand...

Good point whenever having problems go back to basics. Do a simple small clear cast by the book. If that works good then it is something in the process. BUT be sure your temps stay above at least 72 throughout the process.

Let us know what you find out.
 
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