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Discussion Starter #1 (Edited)
Hi

I finished building the projector screen and now paint time.
2.4 x 1.6 meters unbleached un primed cotton artist canvas which measures .53 mm in thickness.
Ceiling mounted IN1503 inFocus Projector (2300 - 3000 Lumen, 1800:1 Contract ratio, 16:10 Aspect).
Conference room 7m x 6m, low-average natural light + florescent lights.
No movies, only educational, tablet and pin (black, blue, red) writing.
I have a spray gun and a compressor and can mix du pont paint since I have their automotive system.

I am at lose with what primer /paint type/color to use. from my reading around (gray color may be best for me.)

Many thanks from Sydney Australia
 

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Hi samjesse, welcome to the forum! :wave:

We haven't messed around much with water-based automotive paints since they are quite expensive compared to house paints, and even artist paints, but there is no reason they wouldn't work for your screen as long as the gloss level is kept very low (as in almost none).

In your application I don't think you need to add any reflective element to boost reflective performance since you are not after the most "theater-like" image you can get, but are only interested in presentation applications.

Your PJ is a bright one and I believe you could benefit from a gray screen to increase the contrast of your image. I am unfamiliar with the gray paints from DuPont, but the more neutral the gray the more accurate your screen image will be color-wise; but again, this might not be a huge concern to you since this isn't for a home theater.

I think I would use a N8 gray screen for you application, but this is just a guess. If you can match your Dupont paints to other colors you might go to a store that sells artist paints and ask them for a tube of N8 gray, make up a sample of that and then match it with the Dupont paint. I'm not sure what artist paint brands are available Down Under, but I know that Golden (yes, that's the brand name) sells paints from N9 to N2. BTW, in the Munsell color system N10 is pure white and N0 is pure black.

As for priming the screen, I am unfamiliar with using canvas and I don't know if you should use a solvent or water-based primer (the water-based might make the canvas shrink).
 

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Discussion Starter #3
I am not keen to use the automotive paint since it is expensive, I would go to the local paint store (Artist paint supplier) and see what advise I can get for primer and neutral gray.

shall I search for white opal pearlescent (which is a water based acrylic )? and mix some with the NG?
 

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I am not keen to use the automotive paint since it is expensive, I would go to the local paint store (Artist paint supplier) and see what advise I can get for primer and neutral gray.

shall I search for white opal pearlescent (which is a water based acrylic )? and mix some with the NG?
Sorry, I misunderstood you on the use of auto paints. We usually use normal house paints as the base for our screen mixes, but our brands are not available in Oz. We have several members here that will hopefully read this and give you some names of paints in your neck of the woods. I would still recommend getting the N8 artist paint to get a sample of a true neutral gray and have it matched at the paint store.

No, I would not recommend adding any pearlescent paint or powder to your screen mix. The only reason pearls are added to paint is to increase the gain of the mix. If too much is added the screen will hot spot and/or have shimmering in bright areas of the image; it also shrinks the viewing cone of a mix so that the screen image will brighten or darken depending on your viewing position in the room. I am assuming that you want a wide viewing cone so that doesn't happen. With your PJ and screen size you don't need to boost the gain of your screen.
 

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Discussion Starter #5
after a lot of reading, I found that Gesso makes a good primer.
A local supplier sells many types, I would like to ask for help in choosing the correct one.
here is the link, opps, I need to have 5 posts of more to post a link.

wholesalecanvasaustralia.com.au click on GESSO OFFERS on the right menu.
 

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This is a tough call for me since I have never used canvas as a screen substrate. If you use gesso as a primer I would use acrylic gesso and get one that is a similar viscosity as house paint (they make some that is more like peanut butter). Here are a few gesso info links:
http://en.wikipedia.org/wiki/Gesso
http://www.aisling.net/journaling/gesso.htm
http://www.goldenpaints.com/products/gessgrnd/gessos.php

The primer that we normally use on screen substrates is a latex primer meant for priming over an already painted surface or bare drywall. My only real concern about using it over canvas is that it might make the canvas shrink. An art store or canvas supply should be able to tell you if it would or not. I'm now thinking it would not since a lot of acrylic gesso I have read about sounds like basically the same thing.
http://www.kilz.com/pages/default.aspx?NavID=22

The idea of a primer is to prepare a surface to be painted. It covers the existing color of a substrate (not an issue in your case), provides a "grippy" surface for the new paint to stick to (again not a problem with canvas) and prevents the substrate from absorbing the screen paint (which I think would apply to you).
 

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Does it need to be painted at all in my case? it is now cream color canvas.
Perhaps not! If you don't really require accurate colors, and most presentations don't, you would not have to paint your canvas screen unless the weave of the canvas was coarse enough to cause a distraction. It's actually hard for me to think about a non-neutral screen since that is so important in a screen designed for HT use.

I guess you wouldn't need to prime the screen even if you wanted to paint it gray for similar reasons.
 

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Discussion Starter #9
One thing, will it show the wood frame on the back of the canvas once the light of the projector shines on the front surface of the canvas?
 

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Discussion Starter #11
Is there a scale for the shade of NG to image brightness in nits?

for example:
N8 was recommended for infocus which will produce 270 nits image.
what about another projector which would produce 200 nits?

The N8 I found here
when clicked, the next page shows almost white which is not what the first page shows. so, which color is N8?

thx
 

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Discussion Starter #12
I found a local supplier:
Primer
Matisse Background Here
either the Victorian or the Pale Gray. not sure how much to buy for spray on the 3.5 square meter canvas.
would 1 liter be enough?

Top coat:
The Derivan Student
mixing 2:1 of Storm Gray : Fluro White which will give a very close to NG N8.
not sure how much to buy for spray on.
 

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Is there a scale for the shade of NG to image brightness in nits?
I don't know of any scale like that and it would be difficult to make one up since screen brightness is only one factor in determining the proper N shade for a projection screen. While screen brightness is of prime importance, other factors such as wall, ceiling and floor colors must be taken into account as well as any potential ambient light from other rooms or outdoors.

for example:
N8 was recommended for infocus which will produce 270 nits image.
what about another projector which would produce 200 nits?
I'm not sure where you got that info, but those are very high screen brightness numbers. 270 nits = 78.8 fL. and 200 nits = 58.4 fL. For those than don't know, nits is the metric value for screen brightness, the U.S. uses foot-lamberts.

If it helps any, we try to recommend our Black Widow™ mix (N7.5) for screens that will get at least 11 to 12 fL. (3.2 to 3.5 nits); but BW™ is quite a reflective mix and under PJ illumination acts like a N8 or lighter screen using regular gray paint.

The N8 I found here
when clicked, the next page shows almost white which is not what the first page shows. so, which color is N8?
The page with the almost white paint on it isn't N8, it's not even close (I get N9.5 with a color picker tool). Golden messed up there. The small splotch is N8.

Here is a color swatch comparing N7.5 to N8.

 

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I found a local supplier:
Primer
Matisse Background Here
either the Victorian or the Pale Gray. not sure how much to buy for spray on the 3.5 square meter canvas.
would 1 liter be enough?

Top coat:
The Derivan Student
mixing 2:1 of Storm Gray : Fluro White which will give a very close to NG N8.
not sure how much to buy for spray on.
I'm a bit concerned about this part:

"Poster Colour Effects
These are best obtained by mixing the paint with plenty of Derivan White, at the same time adjusting the sheen of the paint with Matisse MM5 Matt Medium. Alternatively the finished painting is treated with a coating of one of the Matisse Matt Varnishes available."

It sounds like that paint may not be matt, but have some gloss to it. A little gloss won't hurt, but too much will cause hot spotting of the screen.

As a general rule-of-thumb I like to allow 1 fluid ounce of paint per square foot of screen surface, it's better to have too much than not enough. 3.5 square meters = 37.7 square feet so I would plan on using about 37 to 38 U.S. fluid ounces of paint, which equals just over 1 liter. 1 liter should do the job.
 

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Discussion Starter #17
I found a local supplier:
Primer
Matisse Background Here
In regards to thinning the primer above. I read on that site
"
Use MM26 (Transparent Gesso) mixed with the Matisse Background Colours for a coloured primer with extra tooth for painting and especially as a pastel primer. (Tip: vary the ratio of MM26 to Background Color to vary the roughness, or amount of tooth, in the primed surface.)
"

does that mean the more MM26 the thinner the final mix will be? or the opposite?
 

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In regards to thinning the primer above. I read on that site
"
Use MM26 (Transparent Gesso) mixed with the Matisse Background Colours for a coloured primer with extra tooth for painting and especially as a pastel primer. (Tip: vary the ratio of MM26 to Background Color to vary the roughness, or amount of tooth, in the primed surface.)
"

does that mean the more MM26 the thinner the final mix will be? or the opposite?
If I'm understanding "low-tooth" correctly I don't think you will have to add any MM26 to your background just to lower it's viscosity for rolling or spraying; I think distilled water would work for that just fine. MM26 will increase the "tooth" of the paint which I think means to make it thicker or stiffer so it will stand up when you pull the paint brush away from the canvas instead of flattening out smooth like a "low-tooth" paint would. If the store where you are purchasing these paints from can't tell you for sure call Derivan directly.

I also learned that Derivan paints are quite matt so you might not need the matt varnish either. :dontknow:
 
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