Translucency Experiments

**mechman** · **03-08-09, 06:00 PM**

This will involve different layers of paint by different applications applied to plexi-glass. The two different methods of application will be rolling and spraying. Rolling will have three sets of measurement of 1, 2, and 3 coats each. I will also measure each coat with my micrometer for thickness. Spraying will involve 1-8 coats with micrometer measurements as well. I'm thinking of using white for starters but will probably add a round of tests with a gray as well later on.

The measurements will be made using both the aforementioned micrometer and the spotmeter.

tiddler did something similar to this a few years back but it was mostly empirical. I think it needs to be done again as we now have new equipment that can actually give us hard data to add to the empirical conclusions long ago.

My intention is to get everything painted this week so that I can start gathering data by next weekend or early next week. The data that I will gather will be both the reflected light and the light that passes through as well as the thickness measurements. Does anyone think it would be interesting to get spectro readings of the light passing through the paint? I can do that as well.

Anyways I'm going to save a couple of posts for the data and then I need some input on this!

Digital Caliper

Scale

**mechman** · **03-08-09, 06:01 PM**

Rolled

The tray, roller, roller cover, and paint (2 cups) weighed 988 grams before starting to paint. After one coat on the mirror it weighed 982 grams. And after painting a poly panel it weighed 976 grams. Meaning there were 6 grams of paint used per coat.

The poly panel measured 2.34mm thick pre-painting and was 2.53 after one coat. So one coat of rolled paint is .19mm or roughly .2mm thick.

I used no water with the rolled paint. I used a 1/4" nap roller.

Sprayed

I measured weight after each coating of 6 panels. The panels are 10X12".

Weight of Wagner Control Spray + Paint = 2293 grams
Weight after dusting 6 panels = 2285 grams
Weight after 1st coat = 2255 grams
Weight after 2nd coat (5 panels) = 2227 grams
Weight after 3rd coat (4 panels) = 2203 grams
Weight after 4th coat (3 panels) = 2186 grams
Weight after 5th coat (2 panels) = 2168 grams
Weight after 6th coat (1 panel) = 2158 grams

Seems somewhat consistent/inconsistent! It think there was too much overspray on a couple of these. I started out with 3 2/3 cups of material. After spraying both the plexiglass and the mirrors there was a little over a cup left.

**mechman** · **03-08-09, 06:01 PM**

Data

Paint Thickness

Spotmeter Readings


		The amount of light hitting the screen was 15fL on 100IRE and 3fL on 50IRE

1 coat rolled - 100IRE

2 coats rolled - 100IRE

3 coats rolled - 100IRE

1 coat sprayed - 100IRE

2 coats sprayed - 100IRE

3 coats sprayed - 100IRE

4 coats sprayed - 100IRE

5 coats sprayed - 100IRE

6 coats sprayed - 100IRE

**Harpmaker** · **03-08-09, 06:55 PM**

If you take spectro measurements of the light coming out the backside, but sure to take some readings of the plastic alone since I doubt it will be truly colorless.

Besides the number of coats and thickness, it would be good to try to find the actual amount of paint put on so an approximate "ounces per square foot" figure can be calculated. I find that when I spray a test panel I come real close to using 1 ounce of paint (not counting water used for thinning) per square foot of panel.

Should this thread be in the Developers forum?

**Prof.** · **03-08-09, 07:24 PM**

Now you're talking my language mech..

As you may know, I've been an advocate of translucent screen materials for many years..
My first screen in fact, was an ultra high gain translucent material over a mirror back..

When it comes to paints as a translucent medium, plain white acrylic paint doesn't have a lot of translucency on its own..
It doesn't take much thickness before you loose most of the translucency..

Tests done years ago showed that with just two spray applications of white paint onto clear acrylic, obviated most of any translucent properties of the paint..
Infact many flame wars were started over this controversy (no names mentioned)when people were spraying thin layers of white paint over acrylic mirror..
Some claimed that they were getting high gain screens with this process..Others claimed that it wasn't any better than having a plain white screen..

I believe.. and from my experiments with my Silver Pearl screen..that the plain white acrylic paint is too dense on it's own to be effective, and needs to be diluted and suspended in a clear medium, to give any required translucency..
The amount of clear medium being added determines how translucent the paint will be..
With a fairly high content of clear, this will allow the application of many coats, to gradually acquire the required amount of translucency..

I think the SP screen proves the point very well..To all intents and purposes it looks like a plain white screen, but exhibits the properties of a silver screen, with the inherent gain advantages..

Anyway, that's my thoughts on the matter, so if that's any help to you, well and good..

**mechman** · **03-08-09, 08:09 PM**

Quote:

Harpmaker wrote:

If you take spectro measurements of the light coming out the backside, but sure to take some readings of the plastic alone since I doubt it will be truly colorless.

Good idea! How do you think I can do this? How about this? Use white paint and get a reading from the painted side and then one from the plexi side. From that we should be able to deduce what that value would be.

Quote:

Harpmaker wrote:

Besides the number of coats and thickness, it would be good to try to find the actual amount of paint put on so an approximate "ounces per square foot" figure can be calculated. I find that when I spray a test panel I come real close to using 1 ounce of paint (not counting water used for thinning) per square foot of panel.

Another good point! Measure the volume used. Might be tough with a roller figuring out exactly how much is left in the roller.... maybe I'll try and squeeze it all out.

Quote:

Harpmaker wrote:

Should this thread be in the Developers forum?

I'm not really developing anything.

**mechman** · **03-08-09, 08:16 PM**

Quote:

Prof. wrote:

Now you're talking my language mech..

As you may know, I've been an advocate of translucent screen materials for many years..
My first screen in fact, was an ultra high gain translucent material over a mirror back..

When it comes to paints as a translucent medium, plain white acrylic paint doesn't have a lot of translucency on its own..
It doesn't take much thickness before you loose most of the translucency..

Tests done years ago showed that with just two spray applications of white paint onto clear acrylic, obviated most of any translucent properties of the paint..
Infact many flame wars were started over this controversy (no names mentioned)when people were spraying thin layers of white paint over acrylic mirror..
Some claimed that they were getting high gain screens with this process..Others claimed that it wasn't any better than having a plain white screen..

Very interesting! This must have been before my time at the other place. I know that you were around long before I was but I never saw this. Well now we'll have some measurable proof!

I'll be using Valspar Ultra Premium Flat Enamel (we call it VUPE for short) as the test paint.

Quote:

Prof. wrote:

I believe.. and from my experiments with my Silver Pearl screen..that the plain white acrylic paint is too dense on it's own to be effective, and needs to be diluted and suspended in a clear medium, to give any required translucency..
The amount of clear medium being added determines how translucent the paint will be..
With a fairly high content of clear, this will allow the application of many coats, to gradually acquire the required amount of translucency..

That's kind of the road we've been traveling in the developer's forum. The problem will initially be in finding a true clear medium. Polyurethanes do not cut the mustard.

Quote:

Prof. wrote:

I think the SP screen proves the point very well..To all intents and purposes it looks like a plain white screen, but exhibits the properties of a silver screen, with the inherent gain advantages..

Anyway, that's my thoughts on the matter, so if that's any help to you, well and good..

Prof, your help is always appreciated!

**Prof.** · **03-08-09, 08:32 PM**

Quote:

mechman wrote:

That's kind of the road we've been traveling in the developer's forum. The problem will initially be in finding a true clear medium. Polyurethanes do not cut the mustard.

Mech..The clarity of the medium is not quite as important when mixed with white paint..
The most important aspect is it's non yellowing properties..
Any good quality Clear Matt Acrylic should suffice, or any of the Artists Clear mediums..

**mechman** · **03-08-09, 09:55 PM**

Quote:

Prof. wrote:

Mech..The clarity of the medium is not quite as important when mixed with white paint..
The most important aspect is it's non yellowing properties..
Any good quality Clear Matt Acrylic should suffice, or any of the Artists Clear mediums..

And that is what we've been testing!

Clear Matte Medium. I also have some clear varnish to test as well.

This is going to turn into a sprint the next couple weeks! I need to get this done before all of the screen samples arrive.

**Harpmaker** · **03-08-09, 10:24 PM**

Quote:

mechman wrote:

Good idea! How do you think I can do this? How about this? Use white paint and get a reading from the painted side and then one from the plexi side. From that we should be able to deduce what that value would be.

It depends on what we are measuring. Taking a reflective reading (which is all my spectro will do) would give you a reading for the white from the white side and then by taking a reading from the back side it would tell you how much the plexi is coloring the light being reflected back from the spectro. The plexi would actually be affecting the color of the light twice, once as the light goes through it to get to the white paint on the front, and then again as that reflected light comes back out to the spectro. This is why photographic filters (or even colored cellophane) appear darker when in contact with a white piece of paper as opposed to looking at the paper with the filter at your eye. I hope that made sense.

Ultimately, I think what will matter the most is how much light is actually getting though the paint being tested. This will be a transmission reading, perhaps best done with your light meter (although your spectro can do this type of reading too, you lucky dog

). I would take an incident reading at the white side and then another incident reading (but with the sensor facing the plexi) on the back side. You probably should first take an incident reading with no target, just the light source used, and then put the clear plexi in front of the sensor and take another incident reading to tell you how much light is lost due to the plexi. Again, I hope that made sense.

Quote:

Another good point! Measure the volume used. Might be tough with a roller figuring out exactly how much is left in the roller.... maybe I'll try and squeeze it all out.

If you have a scale that is sensitive enough (I just got one at Aldi for weighing food for $15) , you might be able to simply weight the paint and roller before and after painting, and then weigh a known volume of paint; then start to work with the calculator. The things we do for science!

Quote:

I'm not really developing anything.

Got'cha

**mechman** · **03-09-09, 10:14 AM**

Quote:

Harpmaker wrote:

If you have a scale that is sensitive enough (I just got one at Aldi for weighing food for $15) , you might be able to simply weight the paint and roller before and after painting, and then weigh a known volume of paint; then start to work with the calculator. The things we do for science!

What is the range on this scale Harp? I've seen ones that go up to 55 or 60 pounds but I'd think I'd want something that shows ounces up to 5 pounds or so. Sound about right?

**Harpmaker** · **03-09-09, 02:08 PM**

Quote:

mechman wrote:

What is the range on this scale Harp? I've seen ones that go up to 55 or 60 pounds but I'd think I'd want something that shows ounces up to 5 pounds or so. Sound about right?

I have the Crofton EK3052 digital scale from Aldi. This may have been a special purchase by them and I don't see it on their website. It reads up to 11 pounds and is accurate to 0.1 ounces. I forgot to include something so you could get a sense of scale (pun intended

), but the footprint is about the size of a small hardcover book.

Harbor Freight sells one that seems to be similar.
http://www.harborfreight.com/cpi/cta...emnumber=95364

**mechman** · **03-09-09, 02:40 PM**

Wow! I didn't think it would be digital for that price. I'll check around and see what I can find. I want to get this started this week so I won't be able to order one online. I'll go check out Northern Tool after work or Fleet Farm. They should have something similar to this.

**mechman** · **03-11-09, 05:30 PM**

I did pick up an electronic scale for $15.

Here's the skinny on this:

Three rolled panels and six sprayed.

Measure thickness of each panel
Measure quantity of paint used by weight
Measure amount of light reflected back at the source
Measure amount of light passed through paint

Anything I missed?

**Harpmaker** · **03-11-09, 06:44 PM**

Quote:

mechman wrote:

I did pick up an electronic scale for $15.

Here's the skinny on this:

Three rolled panels and six sprayed.

Measure thickness of each panel
Measure quantity of paint used by weight
Measure amount of light reflected back at the source
Measure amount of light passed through paint

Anything I missed?

Sounds good mech; but I think the light measurements need to be incident and not reflective, that way you know how many Lux are falling on the "screen" and then how many Lux are making their way out the back. Be sure to take a reading of just the clear plexi so any light attenuation it may cause can be compensated for and we know what the paint itself is doing.

The light reflected back at the source is a different animal. It would be good to measure this as well. It would be interesting to see if a solid, primed target painted at the same time would show an increase in reflectance or just show that most of the light getting through the screen mix is just absorbed by the substrate.

**mechman** · **03-12-09, 10:14 AM**

Good point harp. I intended to do that but forgot when making the list. And I'm measuring incident, reflective and lost light.

About the only thing that will be a pain will be the measuring/weighing.

**mechman** · **03-12-09, 03:47 PM**

The first two 10X12" panels are done. One more coat for the third panel shortly and then I'm on to spraying. It takes about an hour for the paint to dry between coats. My garage is 68 degrees Fahrenheit and I do have a ceiling fan running out there on slow speed.

One coat of paint measured .2mm and weighed 6 grams.

**mechman** · **03-13-09, 10:48 AM**

Derailed by new pj!

Should have painting done by noon though.

**Prof.** · **03-13-09, 07:12 PM**

Nice projector mech..

My number one choice also..

**mechman** · **03-13-09, 08:14 PM**

I can't believe how much better it is than my HC3000U!

**Prof.** · **03-13-09, 08:24 PM**

I've seen a $15,000.00 Sim2 projected image, and I'd have to say that it didn't look any better than the Benq!!

**thewire** · **03-13-09, 11:46 PM**

They were talking about the DLP projectors and how there would be some inexpensive (price drops) ones when I was taking my THX training last year. They said they would be good right out of the box if you set the color to warm, then did the contrast, brightness, and other very basic setup routines. They also said that THX recommends not to use BC, mostly due to the fact that the auibidble noise level from the projector would not meet the requirements this way. I'm still working on getting mine installed in the room, but I'm over half way there to getting it up and running.

**mechman** · **03-14-09, 09:20 AM**

Quote:

thewire wrote:

They were talking about the DLP projectors and how there would be some inexpensive (price drops) ones when I was taking my THX training last year. They said they would be good right out of the box if you set the color to warm, then did the contrast, brightness, and other very basic setup routines. They also said that THX recommends not to use BC, mostly due to the fact that the auibidble noise level from the projector would not meet the requirements this way. I'm still working on getting mine installed in the room, but I'm over half way there to getting it up and running.

I can vouch for all of this.

Except for the audible noise from the pj with BC enabled. I didn't notice any audible noise with it enabled. I don't have it enabled as it seemed to produce a slight hint of some video pixellation during a hockey game.

**thewire** · **03-14-09, 12:55 PM**

Quote:

mechman wrote:

I can vouch for all of this.

Except for the audible noise from the pj with BC enabled. I didn't notice any audible noise with it enabled. I don't have it enabled as it seemed to produce a slight hint of some video pixellation during a hockey game.

It must have been a different model that had problems with noise levels. It could have been something to do with economy mode lamp settings, but I was not able to detect any kind of huge difference from going to whisper mode to normal. I read somewhere that the BC was noisey but perhaps they meant noisey with certain sources. Thanks mechman.

**mechman** · **03-14-09, 05:04 PM**

A picture of the rolled panels:

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