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Thread: simple Hi-Tek coating

  1. #13741
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    Ausglock's Avatar
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    I use Mr. Muscle oven cleaner.. Spray it on, leave for 5 minutes and wipe off.
    The really hard areas might have to use a scraper blade.
    Hooroo.
    Regards, Trevor.
    Australia

  2. #13742
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    So, I've put some 20 mesh stainless steel above and below the baking rack of my tabletop convection oven, two layers each, figuring the radiant heat might cause over curing with much higher bullet surface temps versus the bullet core temps measured with k probes inside test bullets.

    Tried three colors at 195C air temp. Starting temps of ~45C from preheating. Time to curing temp 180C was a bit longer than without the screens, which I guess confirms some radiant heating effect and/or also good convection heating. I pulled samples every 30 seconds after two minutes at minimum curing temp, with the k probed bullet, coated with the same color as the pulled specimens, rising to 185C at two minutes, and flattening and dropping some at the three minute samples from repeated door opening.

    Black Cherry:
    Click image for larger version. 

Name:	image.jpeg 
Views:	5 
Size:	35.5 KB 
ID:	268238
    TruBlu:
    Click image for larger version. 

Name:	image.jpeg 
Views:	6 
Size:	37.9 KB 
ID:	268239
    Kryptonite Green:
    Click image for larger version. 

Name:	image.jpeg 
Views:	5 
Size:	38.5 KB 
ID:	268240

    All smash tests seemed fine. The KG I know is acceptable for wipe off, but what do you think of the other two? As you can see, there's about the same amount with all the bake times (each line is a test: fifteen swipes from the same part of the baked bullet on acetone soaked flannel for each line). More time? More heat (the TB has a touch of green, but I know there's more tweaking I can do)?
    Last edited by kevin c; 09-24-2020 at 03:31 AM.

  3. #13743
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    Quote Originally Posted by kevin c View Post
    So, I've put some 20 mesh stainless steel above and below the baking rack of my tabletop convection oven, two layers each, figuring the radiant heat might cause over curing with much higher bullet surface temps versus the bullet core temps measured with k probes inside test bullets.

    Tried three colors at 195C air temp. Starting temps of ~45C from preheating. Time to curing temp 180C was a bit longer than without the screens, which I guess confirms some radiant heating effect and/or also good convection heating. I pulled samples every 30 seconds after two minutes at minimum curing temp, with the k probed bullet, coated with the same color as the pulled specimens, rising to 185C at two minutes, and flattening and dropping some at the three minute samples from repeated door opening.

    Black Cherry:
    Attachment 268235

    TruBlu:
    Attachment 268236

    Kryptonite Green:
    Attachment 268237

    All smash tests seemed fine. The KG I know is acceptable for wipe off, but what do you think of the other two? As you can see, there's about the same amount with all the bake times (each line is a test: fifteen swipes from the same part of the baked bullet on acetone soaked flannel for each line). More time? More heat (the TB has a touch of green, but I know there's more tweaking I can do)?


    Hi kevin C
    I cant open pictures.
    You seem to have made progress with radiant heat prevention.
    From description you gave a minute or so extra in oven should be OK.
    please advise

  4. #13744
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    I'm not very web savvy: I managed to double post and when I deleted one, it took the attachments with it. I've redone the remaining post and the images should be there.

    I did go up to four minutes after hitting 180, but it's also true that the probed bullet temp dropped from opening the door repeatedly, so maybe the curing time really wasn't extended much beyond 2 1/2 minutes (with the door closed until two minutes post hitting 180, temp would rise to ~185, and would drift down with each door opening to under 180 when opening the door the third time at 3 minutes). I just jury rigged supports for the screens; I have extra racks ordered that will let me supplement the mesh with a layer of bullets above and below the baking tray, which should deflect radiant heat and also provide extra thermal mass.

    Hopefully you'll see the images and let me know what you think.

  5. #13745
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    Quote Originally Posted by kevin c View Post
    I'm not very web savvy: I managed to double post and when I deleted one, it took the attachments with it. I've redone the remaining post and the images should be there.

    I did go up to four minutes after hitting 180, but it's also true that the probed bullet temp dropped from opening the door repeatedly, so maybe the curing time really wasn't extended much beyond 2 1/2 minutes (with the door closed until two minutes post hitting 180, temp would rise to ~185, and would drift down with each door opening to under 180 when opening the door the third time at 3 minutes). I just jury rigged supports for the screens; I have extra racks ordered that will let me supplement the mesh with a layer of bullets above and below the baking tray,mwhich should deflect radiant heat and also provide extra thermal mass.

    Hopefully you'll see the images and let me know what you think.


    Yes images can be seen.
    From solvent wipe tests, it seems you were at the edge with final cure.
    The colors that came off with solvent wipe (specifically the TRUBLU) is OK.
    I suspect that an extra minute in oven at about 180-185 will fix the wipe off.
    Don't forget, that you can put back pre-cooked ones into the oven, watch temperatures, and they take them out.
    That should finalize curing and hopefully fix wipe off as well.

  6. #13746
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    Thank you, Joe!

  7. #13747
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    Quote Originally Posted by kevin c View Post
    Thank you, Joe!
    No problems. Happy to help.

  8. #13748
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    Hi all.

    I'm back to trying Hi-tek after being away from casting and coating for over a year.

    I'm trying to get a decent result with candy apple red but i'm not having the same success i had in the past with the old-gold.

    I've tried a few batches over the last few days and i got the same result. They are passing the acetone test but I can scrape the coating off with a fingernail and they fail the smash test.

    10mins at 200c in my oven starts to brown the bullets at approx the 9 min mark so i tried using 8:30 at 200c or 10 mins at 185c and the results were all the same.

    I've noticed that there were some patches on some of the bullets that would not take the coating. Even after 3 coats these patches were still bare lead so i suspect there is some contamination somewhere.

    The bullets are all fresh cast. One batch was cast hours before coating, the second a couple of days before. They were dried in the sun for a few hours before going in the oven.

    I suspect the old towel i drop the bullets onto out of the mold might have some oil or other contamination.

    Can i wash bullets in denatured alcohol or some other solvent before coating? Should i let them dry after washing before coating?

  9. #13749
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    Could be the alloy. Is it one you used without problems before? A member here posted about how acid washing his casts allowed him to HiTek coat successfully with heavy metal contaminated alloy.

    Contamination of the cast bullet surface like you mentioned is problematic. Oils and silicone lubes are both bad according to comments from folks in the know. I'd guess detergent washing and water rinsing would help, but don't have the personal experience.

    Another thought is sizing. Apparently the die sort of burnishes the surface sized and gives the coating less to bond to. That being said I have coated a friend's sized bullets and didn't see any flaking (though he has yet to load and shoot them so it's possible that he'll come to me at some point with questions on how to clean his bore).

    That's what I can think of. I'm sure others will add their experiences on other potential causes for adhesion failure.

  10. #13750
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    You can indeed wash them in solvent before coating, i'd use acetone to give them a good clean to hopefully get any oil that could be present off them. Any oil on them will make the coating not stick or leave a patch that looks like bare lead.

  11. #13751
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    try casting a few and dropping onto paper towel. then try coating.
    Hooroo.
    Regards, Trevor.
    Australia

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check