How much metal flake per quart of paint? - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 8 Old 10-11-11, 05:20 PM Thread Starter
Nak
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How much metal flake per quart of paint?

Has anybody played with mixing metal flake powder as opposed to a paint or binder with the metal flake already mixed in? I know the flakes have to be quite small, much smaller than metal flake paint. How much powder is needed per square foot? Any thoughts on the ideal size flake? Flakes, or spherical particles?

I'd like to play around with screen paint, but I don't want to reinvent the wheel if I don't have to! Thanks!!!
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post #2 of 8 Old 10-11-11, 07:04 PM
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Re: How much metal flake per quart of paint?

Quote:
Nak wrote: View Post
Has anybody played with mixing metal flake powder as opposed to a paint or binder with the metal flake already mixed in? I know the flakes have to be quite small, much smaller than metal flake paint. How much powder is needed per square foot? Any thoughts on the ideal size flake? Flakes, or spherical particles?

I'd like to play around with screen paint, but I don't want to reinvent the wheel if I don't have to! Thanks!!!
No problem Nak, we are here to help if we can.

Reflective flakes or particles for use in making a screen should be between 30 micron and 10 micron in size. Any larger and you will start having problems with sparkles, any smaller and the mix will actually begin diffusing light rather than directionally reflecting it (NASA actually uses glass beads below 1 micron in size to FLATTEN the gloss of paint!).

As to how much particulate is needed depends on the material used and the final results you want. To make long short, you should simply experiment and keep extensive notes.

If your reflective flakes are in powered form it can be quite a challenge to get them into a paint mix without clumping. In the paint industry there are actually special machines designed to do this and IIRC it takes days to get a smooth mix.

If you are literally working with powdered metal be sure the metal won't tarnish when exposed to an alkaline solution (paint) or when exposed to the atmosphere (after it is painted on the screen).

Be VERY careful when dealing with powdered aluminum!!! Unless it has been specially treated by a process called passivation it can react with water (as in water-based paint) in a hydrothermic reaction hot enough to start fires! These reactions can take weeks to occur after mixing. The reactivness of aluminum is the reason paint stores have signs on their paint-shakers NOT to shake any paint containing aluminum!
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post #3 of 8 Old 10-11-11, 08:42 PM Thread Starter
Nak
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Re: How much metal flake per quart of paint?

Thanks! Actually, I was wondering about using silver. http://www.advancedmaterials.us/47MR-12F.htm Kind of spendy, I know. I just had no idea of how much you'd actually need. Looking at it's reflective properties, it looked like a good step up from aluminum. Has anyone tried this? Or is it a really bad idea? I wonder if it would tarnish once suspended in an acrylic medium... My thought would be to mix it with water first, then slowly add the medium.
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post #4 of 8 Old 10-11-11, 10:37 PM
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Re: How much metal flake per quart of paint?

Quote:
Nak wrote: View Post
Thanks! Actually, I was wondering about using silver. http://www.advancedmaterials.us/47MR-12F.htm Kind of spendy, I know. I just had no idea of how much you'd actually need. Looking at it's reflective properties, it looked like a good step up from aluminum. Has anyone tried this? Or is it a really bad idea? I wonder if it would tarnish once suspended in an acrylic medium... My thought would be to mix it with water first, then slowly add the medium.
Good find! The micron size looks very intriguing. As a VERY rough guess I would think that somewhere between 25g and 50g of flakes added to 4 fluid ounces of clear medium (I would use Liquitex Matte Medium) would make something similar to the 4 oz. bottle of Auto Air Aluminum we recommend for making Black Widow™. That silver powder is prohibitively expensive for my wallet however, so I won't be trying it until I win the lottery. As a price comparison a troy ounce of silver is going for around $32.50 so the powder costs far more than the metal value.

A troy ounce (12 per troy pound) equals 31.1034 grams. An avoirdupois ounce (what us Americans use every day - 16 per avoirdupois pound) equals 28.3495 grams.

What would concern me is that silver does tarnish easy. Exposure to oxygen turns it black and sulfur turns it yellow to dark brown.

What Causes Silver To Tarnish? The presence of Hydrogen Sulfide in any material that silver comes into contact with, is one of the prime reasons for silver tarnish. Sulfur containing materials generally cause silver to tarnish and Hydrogen Sulfide is just one of these. Materials like wool, rubber bands, fuels derived from fossils, a few types of paints and rubber (latex) gloves are some of the common materials that cause tarnishing of silver. Certain foods like eggs and onions also hasten the silver tarnish process. You can therefore realize that, touching silver jewelry with oily hands or after a meal could also stain your silver jewelry with tarnish. The extent and speed with which your silver jewelry tarnishes is also related to the climate and in general, high humidity would result in silver tarnishing much faster.
http://www.newsletter.kaijewels.com/silver-tarnish.htm
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post #5 of 8 Old 10-11-11, 11:52 PM Thread Starter
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Re: How much metal flake per quart of paint?

This stuff might be just the ticket! "Silver Coated Aluminium Flecks"

http://cenotechnologies.com/flecks.php

No price given, but should be a bunch cheaper...

Maybe to avoid tarnish mix it just before spraying, then a couple coats of matte Medium after painting to seal oxygen out.
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post #6 of 8 Old 10-12-11, 08:55 AM
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Re: How much metal flake per quart of paint?

Quote:
Nak wrote: View Post
This stuff might be just the ticket! "Silver Coated Aluminium Flecks"

http://cenotechnologies.com/flecks.php

No price given, but should be a bunch cheaper...

Maybe to avoid tarnish mix it just before spraying, then a couple coats of matte Medium after painting to seal oxygen out.
A clear top-coat may retard tarnishing, but I know of nothing that will prevent it. Like almost everything else in DIY screens you simply have to test stuff and see if it works. While we are all about the science of screens, empirical testing has it's place.

Several years ago we were trying to find a source of glass beads in the 10-20 micron range, and while they are available they are expensive and one must buy in something like 25 kilogram increments! I suspect the products from the company above fall into the same category. This isn't a problem if you are a screen mix manufacturer and make your mixes in 1000 gallon lots (or more), but as a DIY solution for the average Joe it just doesn't work.

You seem to have been bitten by the screen mix developers bug! I'll warn you going in that it's a tough habit to break.
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post #7 of 8 Old 10-12-11, 02:02 PM Thread Starter
Nak
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Re: How much metal flake per quart of paint?

I talked to an engineer at the above outfit. The silver coated aluminum isn't an option due to powdered aluminum's explosive characteristics. It has to be shipped in explosion proof containers. He recomended avoiding any type of aluminum powder for that reason.

Another option they have is silver coated glass flakes. Highly reflective, more so than aluminum. Two problems. First, it's 34 micron average size, so slightly above the size range you mentioned. Second, the minimum order is 1 Kg @ around $700 or $800 depending on the cost of silver at the time of order. So, it's half the price of the silver flakes/kilo but you have to order so much you'd need to go in with a group of people. From what you said maybe $70 worth would be enough, so 10 people could go in together on 1 purchase. I might be able to get a small amount as a sample; I'm working on that now.

The engineer was convinced that suspended in a water based acrylic paint and covered with a clear coat of acrylic would prevent any tarnish from forming. However, mixed in a latex paint it would probably tarnish.

What do you think? Is the 34 micron just too big?
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post #8 of 8 Old 10-12-11, 02:18 PM
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Re: How much metal flake per quart of paint?

34 micron is getting up there. To put things in perspective, the older Da-Lite Hi Power screen with a 2.8 gain had glass beads 9 micron in size. I don't really see the 34 micron silver coated aluminum as having that much, if any, real advantage over AAA-F (which I think even has a smaller particle size).

I seriously don't want to rain on your parade, but with PJ's getting brighter every year the day is coming fast when a reflectively enhanced screen mix won't be needed even for 3D.
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