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Tim Bateson
08-15-2014, 5:05 PM
I've engraved - "marked" a number of gun parts. It comes out a brilliant white - as it should. However I have one customer for whom I've had to re-run the markings. Seems the marks are fading when left in the sun. Is this normal or as my guess would be the anodization isn't hard enough?
Someone will ask for a picture - I didn't take any. The brilliant white markings had become faded until just barely visible. I re-ran them back through the laser and they are again bright white.

Mark Sipes
08-15-2014, 5:38 PM
any chance the customer is applying a stain/ protective finish to the parts? Otherwise I would expect the entire gun to be fading..!

Tim Bateson
08-15-2014, 6:34 PM
Following my suspicion, I set one outside today (cloudless day) and the part exposed to the sun sure enough did fade.

Sandy Henry
08-15-2014, 6:42 PM
After you've etched thru the anodize layer, maybe the aluminum oxidized quicker than usual. I think it darkens as it oxidizes. - Just guessing.

Gary Hair
08-15-2014, 8:51 PM
It's possible you are hitting it with too much power. All you want to do is bleach the dye and not disturb the surface. If you don't disturb the surface then there shouldn't be any oxidation taking place because the underlying aluminum isn't exposed. That's what I've been told anyway and I've never really looked into whether it's true or not.

Kev Williams
08-15-2014, 10:41 PM
Well-- Here's some of my experiences with anodizing--

This pic shows portions of 3 anodized control panels I built 4 years ago. For nearly 3 years, they've been sitting outside, against the house, facing east, right next to our water hose. They're there on purpose for UV and weather testing. There's a house behind ours that shades part of the morning sun, but they get maybe 3 hours of full sunlight every day. As you can see, one panel has faded almost back to it's raw aluminum state, while the other 2 have fared pretty well. They haven't changed much in the past year.

But the etching on all panels looks just like the day I did it...

So why are your guns fading to back to black? Like Gary says, could be you're burning the anodizing down to bare metal. However, if that's the case, I'm not sure why you could bring the etching back to white, unless your laser has the power -- My 40 and 25 watt lasers will NOT etch bare aluminum, however, my 80 watt Triumph will. Also FWIW, the panels I have made have enough anodizing on them that I cannot burn thru it with my 40 watt'er no matter how hard I try. But I have run into black anodizing several times that is so light that it's hard NOT to burn thru it. And it looks terrible if it does, because it's not consistent. Your sig says you're running a 35 watt machine, so...? Could be the dye in the anodizing is leaching, regardless of whether you're into bare metal or not. Anodizers can use pretty much anything they want as dye, I've heard that one shop around here has used RIT clothing dye. Can't help but think that would leach! But- I don't know for sure?

All I do know for sure is that I've etched maybe 5000 black anodized plates, panels or other parts in the past 11 years and while I've seen the anodizing fade, I've never seen, or had anyone tell me that any etching I've done has ever faded.

294925

Dan Hintz
08-16-2014, 2:41 PM
The marks cannot be fading back to their original anodized color... the chemistry simply doesn't support such a thing. What is likely happening is the anodized layer isn't of high enough quality, and you're seeing what oxide layer is there begin to deteriorate, allowing some of the original metal color show through. If that's the case, the only real solution is to request a better quality anodizing.

Mike Null
08-17-2014, 8:16 AM
Anodized aluminum will fade in UV light. It's not likely that it is a poor quality anodizing job given that it's on a gun. But some anodizers are not careful with their process and quality can be an issue. I've rejected many anodized aluminum parts for that reason.

Dan Hintz
08-17-2014, 8:39 AM
Anodized aluminum will fade in UV light.

Just so there's no confusion, I'm not suggesting the anodizing itself won't fade with UV, I'm saying the laser mark cannot fade... the only thing it can do is take on more of the characteristics of the base metal.

Tim Bateson
08-17-2014, 7:12 PM
1. As some have suggested - No I would NEVER laser through the anodization - unless requested to do so. That isn't the proper way to laser anodized parts.
2. What is odd is the marking - which was a bright white after the 1st laser, is now just barely noticeable & turns white again when I re-laser it. This is repeatable by placing it in the sun. I've tried rubbing & chemically wiping it after I laser & see no difference, just exposure to the sun seems to cause this fading.

I'm going to talk with my customer tomorrow about the "possibility" of bad anodization. This is sticky situation as it'll be one contractor blaming another. These parts retail for $,$$$ each & I have done hundreds of them, so this issue has got to be resolved. I do know this is their 2nd contractor to provide anodization, so they won't be anxious to have to find a 3rd.

Scott Shepherd
08-17-2014, 7:41 PM
There's more to this story Tim. As Dan stated, it's not physically possible for something like that to "fade". It's black die, it's not hard anodize, it's just decorative. Once you bleach the color out of it, there's nothing there that could turn color. I don't even know how "bad anodizing" could cause it. It's dye. Once it's gone, it's gone.

Now, if it's hard anodizing, I could understand it. You won't mark hard anodizing with your laser. If you tried, you might get a white mark, that could then fade back to darker, because you'd be "frosting" the top but not penetrating the hard coat, but when light hits it, it would be fading your "frosting" of the top coat, but I don't even think that's possible. I was going to suggest it was something other than anodizing, some other similar process for the guns, but you seem to be in the loop with the customer and know that it's just anodizing.

It would be like something that was painted red, then you engrave it and then you say the area engraved is turning reddish again. It's just not possible. There's something else going on here.

Dan Hintz
08-17-2014, 7:55 PM
For clarity... are these "gun parts" firearms or paintball pistols? I'm assuming the latter but wanted to verify...

Tim Bateson
08-17-2014, 9:05 PM
Gun parts anodized Black, Gray, Green, or Red

Mike Chance in Iowa
08-18-2014, 10:08 AM
Just throwing this idea out there as it doesn't hurt to ask. Are they cleaning the gun with any type of oil or something else that could possibly be changing the color?

Tim Bateson
08-18-2014, 10:20 AM
Just throwing this idea out there as it doesn't hurt to ask. Are they cleaning the gun with any type of oil or something else that could possibly be changing the color?

That was my 1st thought too, but no.

Kev Williams
08-18-2014, 11:00 AM
I've engraved hard anodized aluminum for years, I've never had any of the etching change color. It can be finicky to etch if the anodizing is too light, because too much laser can burn it away to the bare metal just like normal anodizing.

The gun parts are a mystery. Could they be ceracoated? I've tool engraved ceracoated AR lowers, but I've yet to ever laser ceracoat...

Scott Shepherd
08-18-2014, 11:03 AM
I've engraved hard anodized aluminum for years, I've never had any of the etching change color.

You sure if was true hard coat? I've hit hard coat anodized with 75W and done nothing to it. Not even a mark. True hard anodizing is VERY hard.

Chris DeGerolamo
08-18-2014, 11:33 AM
I engrave AA firearm components, never heard of this happening. I would be weary of the anodizing. PM sent.

Kev Williams
08-18-2014, 11:46 AM
So the anodizing shops around here tell me! Or their customers who bring their parts in. I know that tool engraving the hard anodized parts I've done is noticeable harder on the carbide tools. There may be a 'harder' hard anodizing I'm not aware of, would be interesting to see some!

I do have a customer who brings me these small anodized parts, ironically enough they just dropped off a half dozen of them just 10 minutes ago which reminded me-- They're jet black, and sometimes- not always, but sometimes, if I hit them with my normal power, they turn no lighter than a dark blue you can barely see. And once that happens, there's no going back. Experimenting once with them I found that I have to hit them with very little power, like 15%, which barely shows up on normal anodizing. The light pass turns them a medium light gray, that's fine with the customer. But if I hit the same part with more power to see if it'll lighten it, instead it darkens it. It could be these are hard anodized, differently than what I'm used to? I don't know, and my customer doesn't know because THEIR customer has them made first.

Robert Walters
08-18-2014, 11:51 AM
FWIW, I googled "UV sensitive anodizing"...

"...Care must be taken as these finishes are more sensitive to UV fade."

http://chicometalfinishing.com/anodize.asp

Dave Demaree
08-18-2014, 2:53 PM
Just a lurker here as I'm not a laser owner (yet), but I do anodize regularly (Type II, not hardcoat). Let's assume this gun was Type II anodized to a thickness of 1 mil. When you laser the part surface, I'm assuming you're only bleaching the upper portion of the anodic layer, as opposed to actually "engraving" down into the pore structure. If I'm mistaken here, my apologies.

That said, I can think of only two scenarios where a bleached surface could darken back to the original anodized color.

1. The anodic porous structure is in poor condition due to dissolution or other reasons, causing the pores to not fully close during the sealing phase. As a result, the dye is slowly leaching out, darkening the bleached areas in the process. However, when this happens, the part normally has issues accepting the dye at all, as the pores will either be too small or too large.

2. The parts weren't properly sealed, again causing the dye to leach out of the pore structure.

A part that hasn't been sealed properly, or that has a poorly formed anodic layer, will often feel fuzzy or sticky to the touch. Do you notice that with the gun?

Like Scott noted, technically what your experiencing isn't possible, but if the laser is not bleaching through the entire thickness of the anodic layer, and you're dealing with a leaching problem, I can see where something like this could happen.

Ron Fairbanks
08-18-2014, 3:00 PM
Have you talked to the anodizer? I have a great relationship with one of the houses in town and we know what each other needs to do a "good" job. We swap business back and forth all the time and having the relationship helps the customer get what they need without the need to blame each other for the engraving being not up to standards. And with anodized finishes being permeable, I tell all my customer that if the engraving "fades" to wipe the engraved (marked) portion with denatured alcohol which brings up and out any oils or protectants (which are not needed on anodized parts). So far this has worked great.

Michael Hunter
08-18-2014, 3:19 PM
If it is oil/dirt getting into the engraving and darkening it then the following might help :

Putting the parts in boiling water for 5 to 10 minutes (after engraving) will (at least partially*) re-seal the anodising and so deter oil etc. from getting in.

* Depends on how much damage the laser has done to the structure of the anodised layer : if only just enough power was used to burn out the dye, then the re-sealing should be quite effective.

Dan Hintz
08-18-2014, 8:38 PM
1. The anodic porous structure is in poor condition due to dissolution or other reasons, causing the pores to not fully close during the sealing phase. As a result, the dye is slowly leaching out, darkening the bleached areas in the process. However, when this happens, the part normally has issues accepting the dye at all, as the pores will either be too small or too large.

2. The parts weren't properly sealed, again causing the dye to leach out of the pore structure.
These have an air of reasonableness on the surface (no pun intended), but dye doesn't migrate like that... it's not in an aqueous solution once dried, so hanging out in a UV-rich environment can't be a migration factor. On top of that, even if the dye was still "wet", it would stain from the outside of the mark inward and show a very obvious migration pattern. Even poorly sealed...

Tim Bateson
08-18-2014, 10:22 PM
Problem seems to be resolved. Talked with both my customer & other contractor that does the anodization. They have been experimenting with a new harder type of anodization. Of-course, I'm last to know. The solution seems to be more power. My early tests have shown revised settings of 600DPI/50S/100P is working, but more testing to come. Other hard anodized parts such as AR-15 Receivers are easily done at 400DPI/90S/90P, often even 300DPI/100S/75P.

As some have speculated, I was only bleaching a very micro thin upper layer. It didn't look any different, but wasn't enough. After a few days it was still visible, but not bright white anymore. This is not your smooth shiny or smooth semi-shiny anodization you see on most gun parts, but a matte almost light absorbing surface.

Thanks for all of the advice and contacts that were sent. This really is a great community. :D

Dan Hintz
08-19-2014, 5:50 AM
Glad you got it sorted, Tim...

Tim Bateson
08-20-2014, 12:12 AM
Update.... The change in the anodization process was not authorized by my customer or to their spec. My customer will today fire the company that did the anodization. This, I found out was the last straw in a long list of many issue the two were having. They found a company that can produce clean, crisp camouflage anodization. Sounds like a cool process. Can't wait to get the first ones in.

Mike Audleman
08-20-2014, 12:14 PM
Update.... The change in the anodization process was not authorized by my customer or to their spec. My customer will today fire the company that did the anodization. This, I found out was the last straw in a long list of many issue the two were having. They found a company that can produce clean, crisp camouflage anodization. Sounds like a cool process. Can't wait to get the first ones in.

Post picts if you can. Would love to see the camo anodication.

Kev Williams
08-20-2014, 1:06 PM
I want to see too. Very time intensive, not going to be cheap...