Thermal aluminium bronze patination...

[Araich]

Anyone had experience with metalised (thermal, or hot/molten sprayed) ali/copper (bronze) and the potential to patinate with traditional cast bronze chemicals?

[sculptorsam]

No, but I would really, really, like to have some experience with that. I wonder how much the setup would cost?

Sam

[Araich]

Well, the reaction to the patination chemicals was much more timid than with +90% copper bronze (more heat made no difference).

Sam, I paid for the service. It's not that technical, the setup, but would require some investment (compressed filtered air, acet/oxy gas, feeder and gun). I've not looked at it seriously since they also do my shotblasting. If I had any money I would do it.

This has been an experiment, and one I've worked on for some time.

[drthulium]

The lighter color of the patina is due to the white aluminum salts generated when forming the patina, think of it as mixing in some white paint into brown, it makes a lighter brown. Higher zinc alloys of bronze have the same effect. Liver on straight copper (a favorite of mine) gets very dark very quickly, so much so then one really should take precautions to aviod a too dark appearance. Pretty much all the color in bronze patina comes from copper salts, (sometimes modified with iron salts) Aluminum, zinc and tin salts are all color less and as a rule of thumb will lighten the patina.

The ol' chemistry degree sometimes pays off ;)

Nate

[Araich]

These metal salts, how are they bound to the parent metal?
Obviously only lightly as it is easy to rub them off with scotch pad and water... if this is the case, is it possible to apply these salts as a paint wash? Then it would matter less what the parent metals composition was.

[fritchie]

These metal salts, how are they bound to the parent metal?
Obviously only lightly as it is easy to rub them off with scotch pad and water... if this is the case, is it possible to apply these salts as a paint wash? Then it would matter less what the parent metals composition was.

Araich - I've been watching theses posts with interest, because a sculptor friend here had two pieces coated in this way, or something similar, about 10 - 12 years ago. I think I mentioned the larger one, a foam coated in a silver color, probably zinc, in an earlier post. The other was a steel ball about 8 - 10 inches in diameter, with a slice removed, coated in either copper or bronze and left natural color.
He’s since moved elsewhere and I haven’t seen anything similar.

As far as attachment of the salts, they probably are bonded at the chemical (atomic or molecular) level, so painting probably won’t work nearly as well, if at all. Conceivably, if they are made fresh and painted immediately, they might bond, as particle size might still be small enough.

And, please do post pictures. This is something others should see.

[drthulium]

These metal salts, how are they bound to the parent metal?
Obviously only lightly as it is easy to rub them off with scotch pad and water... if this is the case, is it possible to apply these salts as a paint wash? Then it would matter less what the parent metals composition was.

The strength that the different patinas are bound to the surface varies with the type of salt (I know shocking...) The bonding is not really chemical at all, most patinas are not substancially different for paints. The major difference is the paint has a binding agent (usually some type of polymer or heavy petroleum distillate) to adhere to the surface. This is why the surface of a metal must be very clean to patina it effectively. Some patinas simply involve spraying a solution of copper salts on a warm metal surface. Others involve chemical reaction with the surface, the end result is the same however, a very thin surface of metal salts. Aluminum forms an exceedingly strong patina (Al2O3, aka chrondum aka ruby or saphire) because the patina forms a network of chemical bonds, similar to glass. Chemically treating the metal surface lets a network bond develop, something that does not typically occur with powder coating. However if the salt being generated doean't form a network bond, then it is just a powder on the surface. Of course just be cause it is just a powder on the surface doesn't mean it comes off easily, ever had dirt on your car? Using a dry cloth to clean your muddy car doesn't work real well!!:)

An alternative method I have been thinking a lot about is to take as acrylic base (epoxy can be added too) and mixing in a lot (30% by weight) of metal powder, paint this on almost anything, let it dry, there you are, fake metal surface! Done right it is quite hard to tell the difference for the real thing. One may even patina the surface.

Anyhow, I'm rambling now, if you what to hear more about metal coloration I have studied up on the different techniques and I would be glad to answer whatever questions...

[fritchie]

The strength that the different patinas are bound to the
surface varies with the type of salt (I know shocking...) The bonding is not really chemical at all, most patinas are not substancially different for paints.
...deletions ..
One may even patina the surface.

Anyhow, I'm rambling now, if you what to hear more about metal coloration I have studied up on the different techniques and I would be glad to answer whatever questions...

Both drthulium and I have chemical backgrounds and I certainly don’t want to get into an argument with him, but there can be a real artistic difference with differing forms of patina.

He is quite right in saying that aluminum oxide, which with traces of other metals constitutes ruby (I’m not sure about sapphire - he’s probably right) is by far the strongest form of patina. Al2O3 has the same packing size and structure as aluminum metal, so the oxide adheres atom by atom to the surface. This why aluminum doesn’t “rust” like iron and decay; the oxide never peels off and is never more than a few molecules thick.

Anodic coloration of aluminum incorporates various dyes into the oxide lattice, so these colors adhere nearly as tightly as the pure oxide, but I have not seen anodic patinas to date which I consider acceptable to an artist. To my eye, they are gaudy and very unpleasant.

As far as the copper and iron salts which color bronze, they do have a different atomic or molecular arrangement from the alloy and won’t bind as tightly, but in cases like this, particle size matters greatly. Very tiny particles have much greater relative area and will adhere correspondingly tighter.
“Liver of sulfur” or potassium sulfide will act as any other sulfide with copper or bronze - it produces various forms of copper sulfide, running from CuS to CuS2, typically CuS2. This is deep black when thick, but looks dark yellow or brown if very thin.

I have serious reservations about painting onto metal surfaces. The binder, unless it can be made almost molecularly thick, looks just like a layer of paint or colored gum. I had this problem several years back when I wanted to combine the brilliance of watercolor pigments with my sculptural shapes. I experimented quite a bit with watercolor binders for paperlike adherents, and eventually coated concrete casts with artificial “papers” which I painted. I like the results, but consider the process most appropriate for relatively large-scale work, as the thickness of the adherent does blur the shape a bit.

I had other problems as well with this technique, mainly intensity of color. I have related these experiences in an earlier thread.

Let’s keep up the trials and discussion. This is the way art advances. But, remember Leonardo. We have only a small percentage of his paintings because he constantly experienced, and most of his experiments didn’t last.

[drthulium]

Anodic coloration of aluminum incorporates various dyes into the oxide lattice, so these colors adhere nearly as tightly as the pure oxide, but I have not seen anodic patinas to date which I consider acceptable to an artist. To my eye, they are gaudy and very unpleasant.
.....
I have serious reservations about painting onto metal surfaces.
.....
Let’s keep up the trials and discussion. This is the way art advances. But, remember Leonardo. We have only a small percentage of his paintings because he constantly experienced, and most of his experiments didn’t last.

When I was typing that reply I got thinking about how broad a topic artistic patination really is, there is a LOT of chemistry involved, goodness it's interesting, I wish more serious research into the methods was done, but the lack of a major commerial product possibility makes funding of this idea difficult (and funding of course rules research interests in chemistry all too often!)
As for the anodic dyes, the chemical process in fascinating, but I agree that they are often gaudy neon colors found in cheap jewerly, and have therefore taken on that image. I wish the colors found in art glass could find their way in to metal work.
I went to a demonstration by Ron Young, http://www.sculptnouveau.com
a few months ago, he has a line of metal containing coatings that can be applied to ceramics, and patinaed just like a real metal surface! I highly suggest purchasing patina supplies through him, he is very free with the recipes and an all around nice guy.
Here's a direct link to the coatings:
http://www.sculptnouveau.com/coatings.html

Nate

[jsimms]

Anyone had experience with metalised (thermal, or hot/molten sprayed) ali/copper (bronze) and the potential to patinate with traditional cast bronze chemicals?

At the start of the thread, araich mentioned metal spraying.

I do this with a Tafa 2 wire spray outfit. It is a little like mig welder, but uses 2 wire feeders such that the 2 wires arc against each other (+/-) and compressd air blows the resulting molten metal onto whatever you want to coat. Zinc melts at a low temperature, so it can be sprayed onto cardboard or whatever. You can then spray bronze onto the zinc, and it will accept a patina well. This method is primarily used to build up worn bearing surfaces or for hard facing plows etc. Not used much by sculptors, but most big machine shops will have one and could do it by the hour and wire cost. They
might not have bronze wire though.

john

There is also an oxy-acetylene method which uses powdered metal and is much cheaper equipment wise, though not nearly the quality or versatility. The Tafa will spray any metal available for mig use.

Check out metal spraying on the web.

[Araich]

Picture as promised...

John, how much does a kit like that cost? I've only seen gas + wire, not an arc driven one.

[jsimms]

Picture as promised...

John, how much does a kit like that cost? I've only seen gas + wire, not an arc driven one.

12,000 to $30,000, but I got mine on ebay for $499. I was the only bidder, probably because no one else knew what it was. A few years ago I found a site that had a number of used machines at relatively good prices. I'll check the favorites list on my old computer and see if I can find the site.

Down your way, I don't know what you might find. At $499 you could ship it to Australia. Maybe not, as mine weighs 800 pounds!
john

[sculptorsam]

12,000 to $30,000, but I got mine on ebay for $499. I was the only bidder, probably because no one else knew what it was. A few years ago I found a site that had a number of used machines at relatively good prices. I'll check the favorites list on my old computer and see if I can find the site.

Down your way, I don't know what you might find. At $499 you could ship it to Australia. Maybe not, as mine weighs 800 pounds!
john

Wow! Nice find. For $500 I'd take one too.

One question occurred to me though. You said the zinc sprayed at such a low temp you could even use it on cardboard. But I wonder about how well it would adhere over steel then. Wouldn't it just "peel" off in a clump when it cooled?

Sam

[Araich]

Ideally you shotblast the steel so that there is good mechanical adhesion.

[jsimms]

Araich is right about blasting prior to spraying on metal. It needs "teeth" in order to get a good bond. (sand or sharp abrasive, rather than bead) With cardboard, you are only relying on the cohesion and thickness of the sprayed material to give a shape. After spraying, the cardboard, wood,foam or whatever could be removed by burning or disolving or whatever.

Hey, if it bonds to a dozer blade, it must bond pretty well to steel!
John

[waveshop]

As for the anodic dyes, the chemical process in fascinating, but I agree that they are often gaudy neon colors found in cheap jewerly, and have therefore taken on that image. I wish the colors found in art glass could find their way in to metal work.

Nate


It is interesting you make this comment. Now I dont know much about anodic dyes but I do know polyester and epoxy and getting an art glass effect with transparent pigments is no easy task but there is potential. I have begun to drop miniscul amounts of metalics into my resin mixes and getting nice refraction effects.

It is one lengthy process, as I am sure Ariach will agree, to spray 11-15 coats of just one or two colors over a piece. The effect you are asking for Nate is possible on metal, I think, but on a very time consuming investment. It takes me two to three weeks to "layer" up my resin coats because they are hand dabbed on very thin. base coat, color dab, full clear coat, color dab, color dab, full clear coat, etc,etc... until the final Hot coat. And I am still not getting the "deep art glass effect" I would like to see

And yes,..... there is the hurdle of the outdoor longevity of this penetrative sun pounding on the polymer. It sucks and I am hunting for that dream batch of "clear" ultraviolet protected resin. Yea,... I know. Dream on. For now I live with the fact that they are inside pieces because just as Nate stated about anodic dyes, The solid pigmenting of polyester and epoxy are neon gaudy,... but thats the set back for ultraviolet protection outdoors, for now.

[sculptor]

I do know polyester and epoxy and getting an art glass effect with transparent pigments is no easy task but there is potential. I have begun to drop miniscul amounts of metalics into my resin mixes and getting nice refraction effects.
And yes,..... there is the hurdle of the outdoor longevity of this penetrative sun pounding on the polymer. It sucks and I am hunting for that dream batch of "clear" ultraviolet protected resin. Yea,... I know. Dream on. For now I live with the fact that they are inside pieces because just as Nate stated about anodic dyes, The solid pigmenting of polyester and epoxy are neon gaudy,... but thats the set back for ultraviolet protection outdoors, for now.

as/re polyester and metal powders:

mermaid (http://home.mindspring.com/~mandali/sitebuildercontent/sitebuilderpictures/figure.sculpture.mermaid.by.figure.sculptor.rod.pa tterson.jpg)
has a combination of dyes and bronze powders suspended in polyester resin-(gell coat) I keep it thick and assume it will fail (by sloughing off the surface) over a lifetime---I hope to slow this down on the mermaid with several coats of clear lacquer overspray--the nice thing about lacquer is that new coats bond with the old--this should slow the degradation significantly.
<br>She is on a house facing the pacificnear L.A.-----lots of sun and salt spray and a bit of L.A's. polution.

Meanwhile, LYNN (http://www.portfolios.com/Pics/sculptor/sculptor_3_p.JPG) has spent the better part of the last 16 years outside with few ill effects-----she has darkened a bit as normal bronze would-----just a tad faster

ISIS (http://home.mindspring.com/~mandali/_uimages/ISIS.4.18.03.37.5.jpg) , unfortunately--because she lives on the truck's campertop,-- is out on the roads being bathed by acid polution and salty water sprayed up from wet road surfaces, so I have to repair and recoat her every 2-3 years.

I think it likely that the denser (in dyes and metal powders)the surface coats , the more they protect the underlying material from U.V. And, several clear coats then protect these "surface" coats from atmospheric polutants.

Don't wait for the perfect resin-----just go ahead and try one.



rod(sculptor)

[waveshop]

as/re polyester and metal powders:

I think it likely that the denser (in dyes and metal powders)the surface coats , the more they protect the underlying material from U.V. And, several clear coats then protect these "surface" coats from atmospheric polutants.

Don't wait for the perfect resin-----just go ahead and try one.



rod(sculptor)


Yes, you will get the protection of the metal underneath it all but the clear coats of resin will continue to cure in the sun and "yellow" over time. Epoxy is the worst for its yellowing properties in UV. Laquer will also yellow, seperate and curl up after only a year or two in the sun. Salt water seems to have no adverse effects on changing resin tint.

Where can I get a Bronze powder? And Anodic Dyes for that matter. I haven't tried either in resin and would like to.

[drthulium]

To avooid the yellowing with sun light youo need to add extra UV protectant, think of it as putting sun block on your epoxy. In the last year or so some really good new chemicals have come out to handle years of exposure to direct sun light.


Yes, you will get the protection of the metal underneath it all but the clear coats of resin will continue to cure in the sun and "yellow" over time. Epoxy is the worst for its yellowing properties in UV. Laquer will also yellow, seperate and curl up after only a year or two in the sun. Salt water seems to have no adverse effects on changing resin tint.

Where can I get a Bronze powder? And Anodic Dyes for that matter. I haven't tried either in resin and would like to.

[waveshop]

To avooid the yellowing with sun light youo need to add extra UV protectant, think of it as putting sun block on your epoxy. In the last year or so some really good new chemicals have come out to handle years of exposure to direct sun light.


The UV protectant I have seen, Either "ambers" or "clouds the resin in the mixing process. If you can direct me to a UV protectant as clear as styrene that is not aerospace pricing I sure would appreciate it.

[sculptor]

Yes, you will get the protection of the metal underneath it all but the clear coats of resin will continue to cure in the sun and "yellow" over time. Epoxy is the worst for its yellowing properties in UV. Laquer will also yellow, seperate and curl up after only a year or two in the sun. Salt water seems to have no adverse effects on changing resin tint.

Where can I get a Bronze powder? And Anodic Dyes for that matter. I haven't tried either in resin and would like to.

OK I get bronze powders from crescent bronze powders company their website
http://www.crescentbronze.com
and from shepard for colors
http://www.shepherdcolor.com

with the color in the resin----they last (or don't) together
as/re uv protection---I keep hoping I'll find a magic bullet and make the stuff darned near eternal

see: MERMAID (http://home.mindspring.com/~mandali/sitebuildercontent/sitebuilderpictures/figure.sculpture.mermaid.by.figure.sculptor.rod.pa tterson.jpg)

hope this is of value to you

rod(sculptor)

[drthulium]

There is a large industry devoted to UV stabilizers, check out BASF's site.

http://www.basf.de/en/produkte/farbmittel/farben/pigmente/publikationen/plastik/techinfo.htm?id=V00-*EL5G4b59bsf3e7

(Paste it in to your browser as one line)

If you up the % UV stabilizer to around 2% (that's a lot of it!) I bet you will not have yellowing worries for some time. Email one of the sales guys with the exact type of coating you want to apply, and the conditions under which it will be exposed (direct sunlight, ocean spray etc.) Tehy will offer up a solution (one of there products of course will work great....) Ask them for a sample to be shipped to you for evaluation, they should send you a nice sized tub, since samples in the polymer industry are usually 5 gallons or so.

If anyone would like help dealing with the big companies contact me and I can help, since I used to work for a big polymer company I know the right things to say. :)




OK I get bronze powders from crescent bronze powders company their website
http://www.crescentbronze.com
and from shepard for colors
http://www.shepherdcolor.com

with the color in the resin----they last (or don't) together
as/re uv protection---I keep hoping I'll find a magic bullet and make the stuff darned near eternal

see: MERMAID (http://home.mindspring.com/~mandali/sitebuildercontent/sitebuilderpictures/figure.sculpture.mermaid.by.figure.sculptor.rod.pa tterson.jpg)

hope this is of value to you

rod(sculptor)