bad merk

[sgimbel]

Does the hardner for Silmar go bad? I poured 4 bottle stoppers yesterday, used 3/4 drops per ounce and it's still real fluid 24 hours later. Temp was high 70's humidity 80/90%. Any ideas?

 

[sbell111]

I believe that the MEKP does go bad. I've had some pours with old resin and catalyst that also stayed mostly liquid after 24 hours. I warmed these under a lamp for a day or so and they were fine.

I then picked up a new bottle of MEKP from Home Depot (who knows how long it was on the shelf) and did a pour using the new MEKP with the old resin and the blanks were hard when they came out of the pot several hours later. (I tend to leave my pours pressurized either all day or all night).

 

[renowb]

Humidity is really high. Don't know if that would effect it or not.

 

[Simplex]

The humidity is one factor but I think you might be a little light on the catalyst. Try using about 10 drops per ounce.

 

[PTownSubbie]

The humidity is one factor but I think you might be a little light on the catalyst. Try using about 10 drops per ounce.

Only if you want the cast to be brittle......

Have you cast the colors before? Some colors inhibit curing. Water also inhibits curing.

If you have more S-41, do a test cast with just clear. In fact do 2 of them. One with a normal amount of MEKP and one with double the amount. This will tell you if your color is inhibiting curing or if the MEKP has gone bad.

 

[Simplex]

The humidity is one factor but I think you might be a little light on the catalyst. Try using about 10 drops per ounce.

Only if you want the cast to be brittle......

Have you cast the colors before? Some colors inhibit curing. Water also inhibits curing.

If you have more S-41, do a test cast with just clear. In fact do 2 of them. One with a normal amount of MEKP and one with double the amount. This will tell you if your color is inhibiting curing or if the MEKP has gone bad.

This is the amount I use and I have not had a problem with my casts becoming brittle. It's also the recommended amount based on the supplier.

 

[PenMan1]

A brief answer to your question. Yes, MEKP does, in fact, go bad. It's demise is hastened by exposure to both air and humidity.

As previously posted, the "additives" to the resin could also be causing a problem. As a "rule of thumb", I try to never add more than 1/16th teaspoon of Mica Pearl per ounce of resin.

A quick suggestion to try and solve the problem with your poured blanks would be to place a 60 to 100 watt bulb directly over the filled mold for at least 4 hours. PR (Silmar 41) will eventually harden WITHOUT MEKP, if left exposed to temperatures above 70 degrees for extended periods of time.

Additionally, 10 drops of catalyst is WAY TOO MUCH for pen blanks. If you read the instructions closely for PR activation, the 10 drop recommendation is for very thin (under 1/16 inch pours). Funny as it seems, with PR, the thicker the pour, the less MEKP is needed. Depending on temperature and humidity levels, I have found between 3 to 4 drops per ounce of resin to be ideal for a solid 3/4 inch PR blank.

I hope this helps.

 

[sbell111]

The humidity is one factor but I think you might be a little light on the catalyst. Try using about 10 drops per ounce.

Only if you want the cast to be brittle......

Have you cast the colors before? Some colors inhibit curing. Water also inhibits curing.

If you have more S-41, do a test cast with just clear. In fact do 2 of them. One with a normal amount of MEKP and one with double the amount. This will tell you if your color is inhibiting curing or if the MEKP has gone bad.

This is the amount I use and I have not had a problem with my casts becoming brittle. It's also the recommended amount based on the supplier.

As I understand it, that is the recommended amount when making very thin casts. For thicker stuff like pen or stoppers, you generally don't need nearly that much to get the job done.

 

[PenMan1]

Just a random thought, here. The humidity level that you posted is VERY HIGH, even by South Georgia standards (one of the most humid areas in the U.S).

Be sure to check your containers of Mica Pearls and pigments. With humidity levels this extreme (especially if you cast in a basement environment), it is VERY POSSIBLE that your "colors" have collected moisture. This will cause havoc with PR casting!

 

[Simplex]

A brief answer to your question. Yes, MEKP does, in fact, go bad. It's demise is hastened by exposure to both air and humidity.

As previously posted, the "additives" to the resin could also be causing a problem. As a "rule of thumb", I try to never add more than 1/16th teaspoon of Mica Pearl per ounce of resin.

A quick suggestion to try and solve the problem with your poured blanks would be to place a 60 to 100 watt bulb directly over the filled mold for at least 4 hours. PR (Silmar 41) will eventually harden WITHOUT MEKP, if left exposed to temperatures above 70 degrees for extended periods of time.

Additionally, 10 drops of catalyst is WAY TOO MUCH for pen blanks. If you read the instructions closely for PR activation, the 10 drop recommendation is for very thin (under 1/16 inch pours). Funny as it seems, with PR, the thicker the pour, the less MEPK is needed. Depending on temperature and humidity levels, I have found between 3 to 4 drops per ounce of resin to be ideal for a solid 3/4 inch PR blank.

I hope this helps.

Thanks for the info. I didn't catch the thin pour recommendation. I'll try changing it up on my next cast.

 

[sgimbel]

I'm using some pigment I got from trukdriver here at IAP. I just put them "on top" of my toaster over and warmed them that way to see what happens. The pigment I'm using is Douglas & Sterns (?) which I have never used before. I just poured 2 more with new MEKP so I should know in a few hours it it's going to start hardening. Thanks all for responses they really help.

 

[Texatdurango]

I'm using some pigment I got from trukdriver here at IAP. I just put them "on top" of my toaster over and warmed them that way to see what happens. The pigment I'm using is Douglas & Sterns (?) which I have never used before. I just poured 2 more with new MEKP so I should know in a few hours it it's going to start hardening. Thanks all for responses they really help.

Speaking of pigments, ya'll do realize that all pigments are not created equal and some pigments and dyes won't work with polyester resin at all and you could be wasting valuable resin experimenting with different mekp drop ratios when all the time it's the pigment not allowing the cure.

 

[PenMan1]

I'm using some pigment I got from trukdriver here at IAP. I just put them "on top" of my toaster over and warmed them that way to see what happens. The pigment I'm using is Douglas & Sterns (?) which I have never used before. I just poured 2 more with new MEKP so I should know in a few hours it it's going to start hardening. Thanks all for responses they really help.

Speaking of pigments, ya'll do realize that all pigments are not created equal and some pigments and dyes won't work with polyester resin at all and you could be wasting valuable resin experimenting with different mekp drop ratios when all the time it's the pigment not allowing the cure.

Excellent observation, George! Unfortunately, I have "observed" these differences "the hard way".

Without going into an extensive list of things that did or did NOT work when mixed with PR resins, I have noticed that some things will work with varying degrees depending on the manufacturer.

I have had excellent results with one brand of acrylic paint as both a pigment and a back paint. Another brand, color and seemingly the same ingredients, purchased from the same store doesn't work AT ALL.

Keeping a "log book" of, not only successes and good recepies, but also including failures helps me to curb the learning costs of PR casting!

 

[PTownSubbie]

A brief answer to your question. Yes, MEKP does, in fact, go bad. It's demise is hastened by exposure to both air and humidity.

As previously posted, the "additives" to the resin could also be causing a problem. As a "rule of thumb", I try to never add more than 1/16th teaspoon of Mica Pearl per ounce of resin.

A quick suggestion to try and solve the problem with your poured blanks would be to place a 60 to 100 watt bulb directly over the filled mold for at least 4 hours. PR (Silmar 41) will eventually harden WITHOUT MEKP, if left exposed to temperatures above 70 degrees for extended periods of time.

Additionally, 10 drops of catalyst is WAY TOO MUCH for pen blanks. If you read the instructions closely for PR activation, the 10 drop recommendation is for very thin (under 1/16 inch pours). Funny as it seems, with PR, the thicker the pour, the less MEPK is needed. Depending on temperature and humidity levels, I have found between 3 to 4 drops per ounce of resin to be ideal for a solid 3/4 inch PR blank.

I hope this helps.

Thanks for the info. I didn't catch the thin pour recommendation. I'll try changing it up on my next cast.

Gary,

I think you will find a huge difference in your cast brittleness. If you don't have a problem with them being brittle, you may find that they work for you but I think they will turn SO MUCH NICER with 3-4 drops/oz. The only thing is it will take a bit longer for them to fully cure.

Let us know how your next casts turn compared to the earlier ones.

 

[Steve Busey]

I did a couple bottle stopper blanks last week that were still gel-like the next evening. I preheated the (shop's) toaster over for just a few minutes, turned it off, then put the blanks in there on a small piece of wood. All was well the next day.

 

[Kingk0ng]

I'm using some pigment I got from trukdriver here at IAP. I just put them "on top" of my toaster over and warmed them that way to see what happens. The pigment I'm using is Douglas & Sterns (?) which I have never used before. I just poured 2 more with new MEKP so I should know in a few hours it it's going to start hardening. Thanks all for responses they really help.

I used the same dyes for the first time Friday, blank was still very unstable after checking it the next morning, put the mold in front of a small electric heater and it finally solidified. I attributed it to adding waaay too much pigment as I couldn't seem to get the color I wanted.

 

[jason_r]

Additionally, 10 drops of catalyst is WAY TOO MUCH for pen blanks. If you read the instructions closely for PR activation, the 10 drop recommendation is for very thin (under 1/16 inch pours). Funny as it seems, with PR, the thicker the pour, the less MEPK is needed. Depending on temperature and humidity levels, I have found between 3 to 4 drops per ounce of resin to be ideal for a solid 3/4 inch PR blank.

I hope this helps.

Thanks for the info. I didn't catch the thin pour recommendation. I'll try changing it up on my next cast.

You might check the data in my Resin Color Library . Even if you're using different pigments, it includes data on amount of catalyst, gel times, temperature, and opacity of the pours.