Hi-tek coating failed - opinions please

[marvelshooter]

My last batch of boolits came out with a very coarse texture almost like sandpaper and I can scrape the coating off with a finger nail. I am getting leading in a 44 magnum revolver with midrange loads after 20 rounds. My process which hasn't changed is as follows. After shaking 3 pounds of boolits in a closed container they are dried for an hour in the sun on a screen. They are then baked in a pid controlled toaster oven for 10 minutes after reaching 400f. They are put in a cold oven and warmed up with the oven. Is this too long? Should the oven be preheated without the boolits?

[DDriller]

Sounds like too much coating and then not cured if you can scrape it off.

[Avenger442]

If I remember correctly, and I'm sure Joe will chime in, rough texture with problem adhering to the lead are usually a sign that the bullets were not dry before baking. But an hour in the sun should have dried them. Assuming you are mixing per directions.

Have you coated this lead before with success? If not it may be some contaminant on or in the lead.

You can also create problems with Teflon used in same area as the coating. But that, I believe, just shows up as a problem with the coating adhering to the lead.

Have you got some photos so we can see what you are talking about?

[marvelshooter]

I will try and post a photo tomorrow. I haven't had good luck posting pics to this forum.

[marvelshooter]

IMG_20260709_073902439.jpg
Best I can do

[Ausglock]

I'd say way way too much coating applied.

[marvelshooter]

I'd say way way too much coating applied.

That makes a lot of sense. When I needed a new batch of coating there was some residue in the bottle I couldn't get out. If that dissolved into the new batch it's now too strong or rich. I will dump this batch and either find a way to clean the bottle or get another.

[Half Dog]

We drink the Lipton green tea. I wash the empties, drill a small hole in the lid, and use that as my mixing/dispensing bottle.

[popper]

Do a really light coat and then a second heavier coat. Cook each coat. Cooking longer will darken the coating but not hurt it. Too high temp will hurt it.
Do the acetone wipe test to insure proper curing. Not dry before baking will cause adhesion problems.

[Noah Zark]

The toaster oven may be a contributor. The coils in the top provide radiant heat in addition to heating the air inside by convection. Radiant heat is more intense and provides faster heat transfer. It's like broiling cookies or a pie instead of baking them -- too hot, too fast, despite the oven temp controller holding 400 F. At work we use a "tent" of stainless steel foil (tool wrap) to block the radiant heat from heating samples too quickly. The samples see 400 F, but convection only.

Noah

[Avenger442]

marvelshooter What ever the problem is the guys here will stay with you to sort it out.

What Ausglock said it looked like to him reminded me of one of my first tries of the coating. Ignoring the thin coat advice I tried to make it a jacket, instead of lube, with a thick coat on the bullets. Well those .45 bullets had to be recast. Coating was flaking off. But I didn't get the rough texture you are getting.

Stick with a thin coat. When following the mix instructions, I actually add a little more acetone, with the first coat you will still see the lead through the applied coating before baking. I usually apply three thin coats on rifle bullets as insurance. But it really isn't necessary. Shooting some 300 PRC bullets right now with only two coats. While I would not recommend it I have shot bullets with one coat with no problem. But that is not the accepted way and may cause leading. I like to experiment.

To answer one of the questions you asked. I preheat my oven before putting coated bullets in to bake. And I put the tray of coated bullets on top of the oven while preheating to make sure they are dry. They usually get hot enough that you don't want to hold one for long in your hand. Probably are already 100F when I put them in.

[marvelshooter]

Update. I started with a new container and a fresh batch of coating and I am back in business. The original bottle was a mess that wasn't getting properly cleaned between batches.

[Ausglock]

Update. I started with a new container and a fresh batch of coating and I am back in business. The original bottle was a mess that wasn't getting properly cleaned between batches.

Great news.
I use 10ML syringes to suck up and apply the coating to the bullets... 6mls to 250 9mm bullets per coat.
This gives reliable repeatability.
the syringes are cheap and come in boxed of 250 and last a long time. 1 syringe will allow me to coat 20,000 bullets before the acetone starts to goo up the black plunger..

[marvelshooter]

Great news.
I use 10ML syringes to suck up and apply the coating to the bullets... 6mls to 250 9mm bullets per coat.
This gives reliable repeatability.
the syringes are cheap and come in boxed of 250 and last a long time. 1 syringe will allow me to coat 20,000 .

Great idea. Thanks

[fredj338]

2 thin coats, i bake in a preheated conv oven for 15-16min. Put the first bake under a fan to dry while i bake the next batch & repeat.

[Petander]

They are then baked in a pid controlled toaster oven for 10 minutes after reaching 400f.

Do you have the PID sensor in a bullet like this so you know the bullet temp?

10 min "after reaching 400 F" is too long IF you mean the actual bullet temp. I clock two minutes after bullets have hit 180 °C (360 F) and my PID overshoots to 370 F in those two minutes. Nothing wipes off with acetone when a bullet is rubbed for a full minute.

I've been told my colours are wrong,I'm no expert. But my Hi Tek bullets shoot clean and good.