Watch the temps!

[BrutalAB]

The other day i was powder coating some boolits with an alloy i had not previously used. I keep my oven set at 450 usually, for reasons I don't remember.
Melted my boolits.
I keep an oven thermometer in there and it never got above 450.
Alloy was (all close estimates)
2 pounds of linotype
.5 pounds of pewter
7.5 pounds of pure lead (enough to fill up the 10 pound pot the rest of the way.)

I figure my thermometer must be off by a bit. Set my oven back down to 400 and even adjusted setting down to 375 for the next attempt.

Think i might check calibration by boiling some water in it.

[Phlier]

How close to the top set of heating elements are your boolits? Ideally, you want the bottom set of elements covered with a solid sheet of metal, then you want to keep your boolits as far away from the top set of elements as you can get. The infrared heat coming off of those elements can really heat stuff up that is in close proximity to them. Stuff can get way hotter than the temperature you have your oven set to if they're too close to the heating elements.

[Conditor22]

The harder the alloy the lower the melting point. Smaller boolits ten to melt easier also

Use a couple of oven thermometers set in the middle of the shelf you will be baking on and check the temperature the oven is set at when the thermometers reach 400°

450° is much hotter than needed. If you have a toaster oven, they are more prone to hot spots because they don't have a circulating fan to evenly distribute the heat.
** the surrounding temperature will affect the final oven temperature due to the location and type of thermostat the countertop ovens use.

[BrutalAB]

Its a toaster oven with a convection setting. I call all counter top sized ovens toaster ovens, so i dunno if i am being entirely accurate calling it a toaster oven.

The hard alloy bullets were on the middle rack, the higher of my two racks. Next batch they were on the bottom.

[Dragonheart]

The melting point of lead is 621 degrees, tin is approximately 450 degrees and antimony over 1100. I would not think 450 degrees would melt any suitable bullet alloy, but for PC you don't need or want 450 degrees anyway as high temps can darken your coating.

I would suggest purchasing a Glass Taylor Oven Guide Thermometer, about $12, as it sounds like your thermometer is about as accurate as your oven thermostat. Place the Taylor where you can see it through the oven glass door and run a test on your oven. First going to 400 degrees and will it stabilize at that temp and hold it without wild swings. If it holds within 10 degrees plus of minus I would call that fair and a useable oven, closer to 400 the better. The glass thermometer reacts instantly so you can monitor your process. Good luck on the next batch.

[Petander]

How close to the top set of heating elements are your boolits? Ideally, you want the bottom set of elements covered with a solid sheet of metal, then you want to keep your boolits as far away from the top set of elements as you can get. The infrared heat coming off of those elements can really heat stuff up that is in close proximity to them. Stuff can get way hotter than the temperature you have your oven set to if they're too close to the heating elements.

Hello Sir Bird,

I just described my bake / bullet temp measurement in another thread. Radiant heat is in the main role, I've been using IR meter to follow bullet temps for a while now.

Bullets get quite a bit hotter than air in my case. Once you learn how,it's easy to figure out a repeatable, good bake.

[Phlier]

Hello Sir Bird,

I just described my bake / bullet temp measurement in another thread. Radiant heat is in the main role, I've been using IR meter to follow bullet temps for a while now.

Bullets get quite a bit hotter than air in my case. Once you learn how,it's easy to figure out a repeatable, good bake.

Yet another beautiful boolit picture! I’m going to go read your thread about temp monitoring right now. I just ordered a four channel thermocouple reader and a bunch of different K type thermocouples to assist in temperature monitoring during the PC bake.

I’m going to try Dragonheart’s idea of casting a thermocouple probe into a boolit, but I’m not quite sure what style of K type probe to use... it seems to me that a thermocouple with a bare end would be subject to grounding issues. So I’m having a hard time finding a thermocouple that has just the smallest bit of shielding that covers the tip, but not so much that it makes it difficult to cast into a boolit.

[Petander]

Yes I'd do the same,a thermocouple inside a bullet. If I was updating with a PID.

My air temp is very steady,I'm doing fine for now. I want a more approppriate oven to begin with for PID. Less radiant heat. I like my 2 kW power though.

I have used cheapo steak meters with their probes inside bullets. But there is a limit how many metering points one wants,my bullets to the right get hotter than the ones to the left etc etc. Inside bullet is different to surface...

[Dragonheart]

The K-type with the bare wires cast into bullets have worked without issue for me. You will find a temperature difference in most ovens especially when you run 4 racks as I frequently do. This becomes very evident when watching the powder flow as some areas will flow while others have not. Trying to get an accurate read with a handheld infrared thermometer is a waste of time and money and opening the oven door defeats the purpose. With the thermocouples you don't need to open the oven door for a reading and you can place your thermocouple in the area that comes up to temp last or use multiple thermocouples as a check.

As far as the temperature variance between the inside and outside of a bullet with a thermocouple is like saying how long does it take for the outside of a thermometer bulb to stabilize. In a perfect world the delay might have some importance, but we don't need that kind of accuracy for a complete cure. I got it from the techs at Prismatic Powder back in 2012; there is some wiggle room, but that can vary with the powder. Just as the techs told me if I use a chrome powder the color is brighter at 450 degrees. If in doubt add a few more degrees or a little more time. My thinking is as long as I get the bullets in the coldest part of my oven up to 400 degrees and keep them there for at least 10 minutes I have got a cure. So what if some areas of the oven get hot faster, those bullets get a little more time, but that is not going to hurt anything. A convection oven will help stabilize the temp as the fan moves the air inside the oven, but is no substitute for accurate monitoring of the temp.

I know I sound anal and I am, but I sometimes cook 5K bullets at a time and I certainly don't want any bullets to come out undercured and certainly not 5K of them, so the little extra effort to monitor the temp is well worth it to me.

[Petander]

Trying to get an accurate read with a handheld infrared thermometer is a waste of time and money and opening the oven door defeats the purpose.

This takes two seconds, $5 and might just help someone from melting their bullets. Might even help getting temps in the ballpark.

[slide]

Petander, as long as it works for you that is all that matters. I think that you will get better results
with Ausglock's thermocouple idea. The thing about it is you are learning everytime you try something. Some of the things I have tried, I look back and say what did I do that for? But, I learned. Carry on!

[Petander]

Petander, as long as it works for you that is all that matters. I think that you will get better results
with Ausglock's thermocouple idea. The thing about it is you are learning everytime you try something. Some of the things I have tried, I look back and say what did I do that for? But, I learned. Carry on!

Absolutely,

I'm just sharing what has worked on a low budget. Not saying this is a better way than any other.

Radiant heat is not very well understood,people talk air temps. I had thermocouples two years ago.

Now I can give you a very exact bullet temp graph from 4.00 to 10.00 min in three locations,left mid and right. One minute intervals. In my oven with air temp @180. I baked 12 batches yesterday. Left and right vary almost 10°C despite a double fan.

[Petander]

I think that you will get better results
with Ausglock's thermocouple idea.

I don't know how this is happening but I'm just suggesting an IR meter to the original poster, and similar situations. Now we are talking about my results and my wrong technique.

I didn't know I have a wrong bake technique or bad results. I didn't mean to steal this thread at all and I apologise.

[slide]

Notice I said think. You may be better off with what you are doing. Seems things work different for different people. No offense intended.

[gpidaho]

Seems to me this is being somewhat over thought. Not a bad thing always but up till now, I've not melted any bullets or even had a batch that didn't cure properly simply by setting the toaster sized convection oven temp to 400 and let it preheat. I use an aluminum !/4" inch plate cut to size as a rack and bake on a silicon mat for twenty minutes, This being with either Eastwood or Cardinal powders.To get the look posted by Petander above, I simply mix a small amount of the color you want with clear powder and get the HyTec look. This is in no way a brag.I can mess up the dream. Simple just seems to work for me. Gp

[slide]

It is amazing how the human mind can come up with ways to do things better. That idea with the clear powder for example. I had trouble with my coatings flaking until I came across Ausglock's idea of putting a thermocouple in the base of a bullet and the flaking went away.

[igolfat8]

Benny,
Out of curiosity, What did the thermocouple teach you? Was your temperature out of range or were you not cooking long enough?

[PJEagle]

One time I placed an oven thermometer in a tray of boolits in my toaster oven and kept the temperature at 425. The boolits near the metal surface of the oven thermometer melted, but the rest of the batch was OK. That was the last time I did that! Now I use a k-type thermocouple connected to a PID to keep the temperature at 425.

[Dragonheart]

Seems to me this is being somewhat over thought. Not a bad thing always but up till now, I've not melted any bullets or even had a batch that didn't cure properly simply by setting the toaster sized convection oven temp to 400 and let it preheat. I use an aluminum !/4" inch plate cut to size as a rack and bake on a silicon mat for twenty minutes, This being with either Eastwood or Cardinal powders.To get the look posted by Petander above, I simply mix a small amount of the color you want with clear powder and get the HyTec look. This is in no way a brag.I can mess up the dream. Simple just seems to work for me. Gp

Good idea about mixing clear with a little color. You get a transparent color assuming the powders are the same type. A base coat of chrome then a top coat of transparent should give some interesting results.

[slide]

igolfat8 I sent you a pm