Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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OPTICAL BLACK ANODIZE / MARTIN BLACK
RFQ: I am looking for a source for Martin Black. I believe it is an anodizing process that produces a non-reflective surface on aluminum. We are looking to coat the inside of a optical cavity.
David K [last name deleted for privacy by Editor]- Calgary, AB, Canada
2000
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
A. Martin anodize, or Martin Hardcoat or Mod Martin is simply an old proprietary name for an anodize / hardcoat system.
Here, we used to do Mod Martin Hardcoat and anodize, and I still could do it, but there is really nothing special about it. We have learned much more over the 30 - 40 years since Martin systems were developed.
I think you should just be looking for generic black anodizing.
David A. Kraft- Long Island City, New York
(2000)
Low Outgasing Black Coating/Plating for Copper or Aluminum
Q. I am looking for a black coating or plating to be applied to sheet aluminum or sheet copper. This plating must be low outgassing, as this is a vacuum application.
In a recent issue of a mechanical design magazine, an article claimed that an optical coating called "martin black" was such a vacuum compatible, low outgassing coating. A web search on "martin black" led to this site. Various letters talked of its optical qualities. One claimed that this term is a shortening of "Martin Marietta Black", and another claimed that this is just "plain ol' black anodizing". Are "martin black" and black anodizing (black oxide?) all the same? If so,I've been told that black anodize has bad outgassing qualities. Does it?
Any info/insights are greatly appreciated.
Thanks In Advance,
Frank Modica- Princeton, New Jersey
2000
A. If the application is for heat absorption or reducing reflection, I could suggest a couple of ways. Black anodizing will do as well as black chrome. However, we have also used a vacuum compatible graphite paint. This one is easy to apply repeatedly using a brush and remove by rinsing. I had found the vendor at the SVC conference four years ago. Unfortunately, I have run out of it and I need to find it again. Since I will be attending the conference again next week, I will let you know if I find it again.
Mandar Sunthankar- Fort Collins, Colorado
Q. Mandar - Did you get the contact? Thanks.
Paul KochendorferMRC - Laguna Hills, California US
A. Unfortunately Paul, No. I asked several vendors there but no luck.
Mandar Sunthankar- Fort Collins, Colorado
A. Try Acheson Colloids. They provide a low gas black. Product name is RW9932.
Robert KillionCentral Coating Company - WestBoylston, Massachusetts
A. See US patent 4111762 and related patents.
It is made essentially by shaping the surface (like an anechoic chamber but with much smaller features) and then helping the light trapping with a black finish, e.g., black anodization.
Carlos ZarateSt.Catharines, Ontario, Canada
RFQ: Looking for a supplier of "Martin Black" coating (or Martin Marietta Black). It is a coating with very good optical qualities.
Thanks,
John V [last name deleted for privacy by Editor]- Boston, Massachusetts
2001
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Multiple threads merged: please forgive chronology errors :-)
Q. I AM A ANODIZER OF 21 YEARS. ONE OF MY CUSTOMERS IS ASKING FOR OPTICAL BLACK ANODIZE. WHAT IS OPTICAL BLACK? I REALIZE THAT IT IS A REFLECTIVE MATTER. CAN YOU HELP ME? THANK YOU.
JIM KLEINmetal finisher - GRANTS PASS, Oregon USA
2000
A. Hi Jim,
In my assumption, optical black is a non etched surface, black anodized. I have done this before for some people and that's the way they specified it. It might be more detailed than this, such as a bright dip pre-finish before the anodize, but they requested it in this fashion. Take it with a grain of salt, I'm just doing my best to spur thoughts and possibly solutions
Matthew Stiltnerplating company - Toledo, Ohio
A. Someone requesting optical black anodize is probably working with optics, such as in some type of camera, telescope, etc. A primary concern in this type of work is stray light, such as might be reflected from a bright shiny surface, and so a black, matte, non-reflective surface on peripheral areas is preferred.
John F. Brewer- Akron, Ohio
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Interesting you mention this John. Like I originally stated in my response, this is what was requested of me. I guess it's 6 of one and 1/2 dozen of another eh? I guess your response makes more sense to me than the bright finish does, based on your examples. But again, I just play by the rules laid out to me by the customer. He was using the parts on a high powered telescopic device of some sort. I see advantages myself to using both finishes frankly. The bright glossed surface providing for more reflection and scattering of the lighting, and the non glossed finish for doing the exact opposite. Matthew Stiltnerplating company - Toledo, Ohio I suppose you hit it on the head, Matthew: whatever rules the customer lays out for you as Optical Black is what you should provide. John F. Brewer- Akron, Ohio 2000 |
A. I would have to agree with John that typically "optical black" would be non-reflective, as is the case for a customer that I anodize parts for now. However, since you have two good but differing opinions on what "optical black" means, your customer may have be more specific, reflective or not. Good Luck.
Lamar Jackson- Fort Walton Beach, Florida
A. Optical black means there is an absence of returned light (near zero reflection). If you look inside a camera, all light reflection is suppressed using the optical black coating. This coating is dull. This could be either anodization or black chrome, I do not know. It does not get easily scratched, that I know.
Mandar Sunthankar- Fort Collins, Colorado
A. Optical black means a minimum of reflection, both specular and non-specular reflection, this means black and as matte as possible. The best results are from a very matte etch or bead blasting and using a good black dye. There is I recall a Martin Marietta optical black process specification which has been used.
Leo Herrington- Grand Rapids Michigan
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plating company - Toledo, Ohio Hi, Matthew. Now that you've apologized for being wrong, I'll chime in on your side :-) What's the difference between a matte white surface and a mirror? If chosen correctly, they may have exactly the same reflectivity, but the reflection from the white surface is thoroughly diffused and scattered whereas for the mirror, the angle of incidence equals the angle of reflection so it can form an image -- it's 'shiney' right? Now, by definition, a black surface reflects very little to no light, right? And if no light is reflected, what difference does it make whether the reflection would have been diffuse or not? The concept doesn't even have any meaning: if it's truly black, it's neither specular nor diffuse, it's just black :-) But, sure, it's much easier to achieve a very black surface on a matte profile than a polished one because a portion of the light will bounce from one black spot to another, offering multiple chances for absorbing the light, "like an anechoic chamber" as Carlos said :-) Regards, Ted Mooney, P.E. RET Striving to live Aloha finishing.com - Pine Beach, New Jersey |
A. Optical Black Anodize is an electrolytic process and uses an inert metal compound. This coating replaces the conventional organically dyed coatings where thermal stability, UV degradation or reflectivity are an issue. This process can be used only with 6000 or 5000 series aluminum alloys. We use this process for our UV Laser Optics.
Cater D. Carroll- Portland, Oregon, USA
A. Optical black anodize is a proprietary coating developed by my company in Sherwood Oregon for use by the optical industry where low reflectivity, low outgassing and U.V stability are desirable with the durability of a conventionally anodized surface.
Richard Brehtertonanodizing company - Sherwood, Oregon, USA
2001
If you feel that your company has trademarked the phrase 'Optical Black Anodize', Richard, let us know and we'll be happy to mention it and credit it! But I doubt that other anodizing shops will concede this widely-used phrase to you without some proof; it seems to be pervasively used in the literature and in patent citations such as in the 1977 Martin-Marietta patent referenced above.
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Martin Marietta "Optically Black" anodize is outlined in US patent #4,111,762 (expired) which can be downloaded from the USPTO website.
Michael Lines- Provo, Utah, USA
2003
Ed. note: Michael had included a direct link, but unfortunately and typically, the link no longer works
Multiple threads merged: please forgive chronology errors :-)
Black body coating alternative to Enhanced Martin Black
Q. Hi,
I am a final year student at the university of Hertfordshire and currently working on my project. I am currently looking for a comparable performance/process and cost of a High emissivity coating which is good for space use, i.e. No/low outgassing, resistant to vibration etc... compared to Enhanced Martin Black.
Can anyone help?
Cheers,
Andrew LewisUniversity of Hertfordshire - Hemel Hemsptead, Herts, UK
2002
Q. Andrew,
I have nothing new at the moment about black body coatings, but I would like to know if you received other replies or worthwhile suggestions. I will be actively searching for methods to produce such coatings, including physical vapor deposition methods.
- Boulder, Colorado USA
2003
Vacuum Compatible Paint
Q. I am studying the reflectance properties of minerals in ultra high vacuum, with light white and infrared from 25,000-600 cm^-1. I am having problems with stray light bouncing off the wall. I tried to spray down the chamber with a vacuum compatible graphite spray. However, although it is improved, I would like to make the walls even darker. I heard about this Martin Black substance and wanted to know if it was vacuum compatible at say 10^-10 Torr and if I could bake my chamber at like 10^-7 with it in there and if so where I could get it. If Martin Black is not compatible or if you know of something better, please advise me.
Thank you for your time.
Mark LoefflerUniversity of Virginia - Charlottesville, Virginia, United States
2003
A. I don't know if this will work for your application (I have not used it myself):
www.lord.com/products-and-solutions/coatings/aeroglaze-z306-polyurethane-coating
V-Glass - Pewaukee, Wisconsin, USA
July 6, 2015
Ed. note Feb. 2023: Early readers thanh Peter, but unfortunately this link is now just more web litter :-)
RFQ: Please advice where can I purchase "Martin black" paint or LORD Chemglaze/ aeroglaze? I need it for my optical housing (visible).
Thanks,
Oded WigdersonMedical imaging - Haifa, Israel
2004
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
A. Hi, Oded.
We appended your inquiry to a thread that partially answers it, where you see that Martin Black isn't exactly paint. Topic 1670 addresses the Lord Chemglaze/Aeroglaze question. Good luck!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Martin Hard Coat Problems
Q. We use a Martian hard coat process for hard anodizing aluminum (sulfuric acid solution saturated with CO2 at 32 °F. Most of the time the color of the oxide is green. Occasionally, we get back coatings. Some of our customers want the black colored coating but we are not able to reproduce the color. Recently we anodized some parts which the customer says are both 6061 aluminum. One group of parts come out green and the others black. Can anyone tell me what can cause the color variation? How can one get black hard coat.
Thank you for your help.
Best regards,
Aysun ScottPlating Shop - Kansas City, Missouri, USA
2004
A. Any color variation you get in un-dyed hardcoat is directly attributed to the alloy of the aluminum & the thickness of coating.
If two parts are run in the same load and come out different colors they are most likely different alloys.
To get black hardcoat you can dye the parts after hard anodizing & then seal them, just remember that when you dye & seal you lose abrasion resistance.
David A. Kraft- Long Island City, New York
? Is the material extruded or machined from extruded bar stock?
Chris Jurey, Past-President IHAALuke Engineering & Mfg. Co. Inc.
Wadsworth, Ohio
Thank you for your comments. We do not know if the material is machined from extruded bar stock. A lot of times we don't even know what type of aluminum we are getting.
Best Regards.
Aysun Scott [returning]- Kansas City, Missouri, USA
2004
Hi Aysun. As long as you realize that attempting to hard anodize unknown aluminum alloys is a problem that must be corrected, and you're working on fixing it :-)
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
! Detailed description of various optical black coatings - including Martin Black - is at
www.optics.arizona.edu/optomech/papers/persky%201999.pdf
Jim McCann
aerospace - Tucson, Arizona USA
April 25, 2011
Ed. note -- July 2015: Sorry, that link is now broken. Readers: links almost always have a very short life compared to our pages (on line since 1989). If posting a link, please try to include the title of the article, or even an abstract, so people can find it.
Regarding the invalid link to the Persky paper, here is a new link:
http://fp.optics.arizona.edu/optomech/papers/persky%201999.pdf
The title of the paper is "Review of black surfaces for space-borne infrared systems" by M.J. Persky. It was published in Review of Scientific Instruments, Volume 70, number 5, May 1999.
Q-Value Add - Penang, Malaysia
February 19, 2016
Ed. note: Feb. 2018: Thanks Dan, but whack-a-mole continues. Links on the internet have deteriorated to nonsense, but readers can try this one now:
https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/persky-1999.pdf
A. I am a retired electrical engineer. I worked for 20 years at Lockheed Martin, and Martin Marietta before they merged with Lockheed. I often worked with optical engineers on spacecraft. They needed better optical black surfaces than simple flat black paint could produce. It had to be as close to zero reflective as possible and it had to be vacuum proof. Also, it had to not degrade with time or light exposure. A coating was developed called Martin Black. Later, a small number of people left Martin and started a company in Boulder where they perfected an even better coating for this purpose. I don't remember further details (see my first statement)
Woody Brison- Littleton, Colorado, USA
January 22, 2019
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