Is Over Curing PC As Bad As Under Curing PC?

[Phlier]

There have been a lot of posts/threads lately about the negative effects of under curing PC. Let's talk a bit about the other side of the issue, over curing.

How is it recognized?

What are the bad effects of it?

Is it easily done, or do you really have to extend your cook time a lot?

Is it worse than under curing?

I'm not talking about using too hot of an oven, I'm talking about leaving the boolits in the correct temperature but for too long.

[FLINTNFIRE]

I would be interested in this also , I have not overcooked any yet , but if it happens , I would like to know if it has any negative aspects .

[slide]

IFS coatings is right down the road from me. I talked to the quaility control head honcho. He said it was ok to go over a little but under cure was a bad thing but, he didn't want to give me a temp that you go over to. I don't know depending on the pmt if it calls for 400F maybe 415F

[Carrier]

I guess if your bullets turn into a puddle probably over cooked. I have tried this and left some in for 40 minutes instead of the recommended 20 and found no issues. I have my oven hooked to pid controller and temp probe mounted inside. It keeps a very narrow temp ban.

[slide]

It has been discussed quite a bit. The a.t.m. (Ausglock's thermocouple method) works well for me. I know what my bullet temps are and it is not expensive. A lot of guys have developed other ways that work well for them. A.T.M. is another option. I hope to have a p.i.d. someday. Just coming out of a divorce and money is tight!

[gpidaho]

I've forgot a batch when distracted. I left it in the oven at 400 for an hour with no ill effect other than a little darkening of the color. They shot the same as any other PC'd bullets. Gp

[Phlier]

It has been discussed quite a bit. The a.t.m. (Ausglock's thermocouple method) works well for me. I know what my bullet temps are and it is not expensive. A lot of guys have developed other ways that work well for them. A.T.M. is another option. I hope to have a p.i.d. someday. Just coming out of a divorce and money is tight!

I'm not talking about methods to make sure that you are cooking at the right temps and for the right duration... yeah, that's been discussed a lot, and I use a four channel thermocouple reader, a thermocouple cast inside a boolit, an oven thermometer, and a good convection oven.

I'm talking about what bad things happen if a batch should get over cured.

[slide]

There are tons of stuff on the internet about what you are asking. Remember that coating bullets with powder coat is still in the infant stage. We are all learning. Overbaking, the powder coat becomes brittle and when the bullet hits the forcing cone it comes off thus causing leading and accuracy problems. Under cure, the coating can do the same thing. Look it up!

[charlie b]

So, what is the answer? Which mfg shows that information on time and what is too much time?

I am interested in heat treating the bullets after PC, so an hour or so in the oven at the mfg specified cure temperature. Will that harm the coating? FWIW, it will also involve a water quench at the end of an hour in the

[slide]

All mfg's should show pmt for whatever powder you have bought. Honestly.I don't know about the heat treating. I would suggest you call the mfg where you bought it and ask them . That way you will have it straight from the horses mouth as they say. Nobody knows their product better.

[charlie b]

About all I could find on the mfg sites were cure times and temps. I did see two cure 'maps' and they were 'open ended' at some temp settings, eg, you could cure the powder at 350deg for as long as you want, but, at 400 you had to limit it to 25min. Unfortunately that is too low for heat treating. The good part is I could heat treat first and then use a longer cure at lower temp to not anneal anything. So now to find specific information about the powder I use.

There was also a lot of discussion at mfg web sites about 'difficult' shapes of parts, where one section heats up faster than another, so you have to 'manage' the cure temp so you have enough time for the thick sections but not overdo the thin sections.

The main thing I noticed is the one cure time and temp listed by many suppliers is not absolute. It is typically the lowest temp with the fastest cure time, ie, you can use a higher cure temp but it won't make the process go faster. I do understand this as most people want to know how fast they can cure the parts and the minimum heat required to do so (economy of time and electric bill).

You can also use a lower cure temp but it will take longer. And there are also some low temp, long cure time combinations that work. Some of those were specified for materials that could not be heated to a higher temp.

[popper]

I over Tempd dome, coating shrunk slightly and split - lost adhesion to the lead. No idea of the temp.but lead didn't melt. Basically, PC fell off.

[slide]

Well Done Charlie b ! Thanks Popper,you are one of the pioneers in the coating world. Not saying you are old.

[Dragonheart]

As I have said many times I got into PC in 2012 knowing nothing more that what a fellow club member told me about the process for coating bullets. I spent a lot of time talking and visiting with commercial applicators, powder manufacture techs at Prismatic Powder and evens some physicists. All were professionals in the PC field, but no one knew anything about powder coating bullets, especially shaking them in a Cool Whip container.

When we discussed the curing it was stressed the importance of time & temp and starting the timing when the substrate reached temp, but they indicated there was some "wiggle room". The answer given me about over curing was, adding more time is preferable to overcuring at a higher temp. The over curing time before problems occur is powder specific, so that varies with the powder, there is no across the board answer. However, my observations over the years going longer on the time at 400 is less of a problem, as I was told.

I once had a batch of Prismatic "Tractor Green" cook all day because I was in a rush and forgot to set the timer. They darkened, but when shot they still maintained a bond and did not lead. I certainly would not recommend doing this, but short of solid information on the subject I think assuring bullets are not under cured is much more important. I have no idea where to find powder specific over curing information on a powder. Even so what we are doing with PC is very different than coating a motorcycle frame. I would suggest if this really causes you concern a "smash test" should confirm the bond and electricity and a scratch test with a 2H pencil should confirm hardness enough for our needs.

[slide]

This stuff will drive a guy crazy. The answer is simple. If what you are doing is working for you then keep doing it. If you feel you are having problems then try the A.T.M. It will only cost you around twenty bucks to set up. A lot of our info is from companies. They powdercoat different metals. These guys are pros,this is what they do for a living. The one thing that we need is the pmt and a way to measure it. We got that if anyone chooses to use it. Just relax and enjoy the ride. This is a hobby not a job. Everybody is different some like to get into all aspects of what they are doing some don't. I feel like we are overthinking this thing!

[Phlier]

Slide, it kinda seems like you’re either annoyed, pissed off, or both in this thread. I didn’t mean to make anyone mad by asking how to diagnose over cured PC and what the effects of it are/were. My apologies for hitting a nerve.

I’m not having any difficulties with my PC’d boolits and haven’t had in the nearly four years I’ve been doing it. I’m just curious. I like to find stuff out. I thought this was the place for that.

Many thanks to those that took the time to post useful information here. Very much appreciated.

[slide]

I am too old to get mad about anything. No offense on my end. I did tell you about over and under cure. I had to look it up myself. If what you are doing is working then stay with it. The best knowledge gained is the knowledge you find. I might not know what I am talking about!!!!

[Dragonheart]

Phlier, are far as I am concerned you asked a very valid question because I asked that same question years ago. As stated, I never got what I would call a definitive answer because I gather you would have to be asking about a specific powder. I think there are about six different powder bases and then different pigments and additives to develop different properties. For this reason mixing powder may produce unwanted results.

I asked a polymer physicist what he thought the best powder would be for coating bullets a he said a "Polyester Base" would most likely be what I wanted. I will say over the years and using a few dozen different powders, mostly polyester base, I think you could go with a much longer cure time and do no harm, but there would not be any benefit either.

As a side note I have some "Bright Chrome" powder I use to spray tools and the like and it cures at 450 degrees for 12 minutes, so there are some powders that have a different cure schedule.

[JWFilips]

Since I PID'd my oven I know the temps are accurate.....Undercooking is bad but over cooking at the "nominal temperature" will hurt nothing!....