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File under "I really need to get a life when"...
Was sitting in an auditorium the other day getting trained on prevention of sexual harassment... anyway, while doodling on my notepad, I noticed how reflective the doodling was. Got me to thinking about my dream of a DIY grey acoustically transparent screen... thought powdered graphite might do the trick without clogging the holes needed for audio transparency (as paint would without extreme care). Has anyone tried powdered graphite as a reflective agent on ANY surface or in any paint? I'm guessing it is far from neutral, sure would be a hoot if it were neutral though. </crazy>
 

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If thinking like that means you're crazy Doug all I can say is Welcome to the club! :bigsmile:

I did do some very limited experimentation mixing some graphite I had on hand with paint and the results were less than promising. I'm not saying that further testing would prove fruitless, but after reading your post I did a bit of investigating on graphite and I'll tell you why I don't think this is a viable DIY screen additive.

My little experiment was to add some seed-lubricant graphite to Kilz2. The resulting mix pushed blue quite hard, but that is easily correctable if you know proper color theory and can measure mix color. :nerd:

The first problem was that graphite is MESSY! The stuff is a dark gray, very light powder and wants to get places you don't want it to go. This attribute is one of the things that makes graphite such a good dry lubricant.

Another problem was that the painted surface appeared to have small black dots in it that were not very reflective at all, which could have been caused by either the size of the graphite particles I was using or that the graphite wanted to clump together in the paint.

Yet another problem is that the paint was very susceptible to changing appearance if it was touched after the paint dried. One of the physical properties of graphite is that it is VERY soft and I suspect that anything exhibiting more pressure on the paint more than a feather duster would cause the graphite at the very top of the paint film to smear. This changes the appearance of the paint, it becomes darker and more reflective, but only in areas that have enough pressure applied and the appearance change also corresponds to the amount of pressure applied. This means getting an uneven appearance to the screen.

In looking deeper into the characteristics of graphite I also found that it exhibits bireflectance and reflection pleochroism in plane polarized light. This mean that polarized light reflected from it will vary in both brightness and color depending on it's polarization. I see this as a negative thing if using such a screen with a LCD projector.

One last characteristic of graphite that means we at HTS won't be experimenting with it any time soon is that graphite is also corrosive to aluminium in the presence of moisture. We like to use some form of aluminum as the reflective ingredient in our paint mixes and aluminum and graphite don't play well together at all. In fact, just making a mark on a piece of aluminum with a regular pencil will cause the aluminum to corrode where the pencil line is!
 
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