Mirror Experiments

**Richum** · **03-12-09, 08:46 PM**

"I wouldn't get too hung up on mirrors. My hypothesis has been that they will do little if any to help vs the problems they create."

Actually mechman I have played with standard glass mirrors (using 12"x12"tiles) in the past and I tend to agree with you that they do little.

However it seems to me that it is all about the the thickness of the layer and the topcoat applied and that it is a delicate balance. I doubt that rolling will ever give the layer thickness control required, no matter what topcoat is used, it just seems to me to negate the mirror and that any substrate would do as well.

I have used different paint concoctions found elsewhere and also some of my own. In theory the mirror should be beneficial but I have not found that to be the case with second surface mirrors. I search for the "plasma effect" or said another way the glow. So I thought perhaps a first surface with a precise thickness of the correct topcoat?

At present I have a white plastic translucent screen (used for lit signs) painted with cream and sugar and it does a decent job, but it just doesn't present the contrast that BW does and I miss that. I am tempted to strip the cream and sugar and paint it with a paper thin coat of BW.

Believe me I have more pressing issues, but this home theater thing is addictive

**Harpmaker** · **03-12-09, 09:49 PM**

Hi Richum,

As you have found, C&S won't give the same contrast enhancement as BW. Such enhancement, as well as ambient light performance, is due mainly to the darkness of the mix; C&S is too light to provide much of either, but it will be better than a white screen.

The more transparent a mix is the more likely it can be used on a mirror with success, and we have only begun to experiment with mix transparency.

It will be almost impossible to get a "plasma effect" from a front-projection screen; there is just too much difference between an emissive device like a plasma TV (it actually generates light) and a reflective device like a front-projection screen (it can only reflect what light hits it). I know some have claimed such performance, but I take those claims with a large dose of salt.

**Richum** · **03-12-09, 11:35 PM**

Quote:

Harpmaker wrote:

Hi Richum,

As you have found, C&S won't give the same contrast enhancement as BW. Such enhancement, as well as ambient light performance, is due mainly to the darkness of the mix; C&S is too light to provide much of either, but it will be better than a white screen.

The more transparent a mix is the more likely it can be used on a mirror with success, and we have only begun to experiment with mix transparency.

It will be almost impossible to get a "plasma effect" from a front-projection screen; there is just too much difference between an emissive device like a plasma TV (it actually generates light) and a reflective device like a front-projection screen (it can only reflect what light hits it). I know some have claimed such performance, but I take those claims with a large dose of salt.

I find C&S to be a good mix and as always it seems to be the trade offs that prevail, BW in my opinion lacks the brightness I seek and C&S lacks the contrast. What to do?

Yes, a mix that is more transparent is key but somehow we must retain the properties of the mix such as accurate color without pushing green or red and so on. Oh well.

I agree, it is not likely to ever obtain a plasma like screen, but if we had a mirror/topcoat that could give the appearance of doing so.....

Imagine the bragging rights!

**mechman** · **03-13-09, 10:47 AM**

I kind of took a detour last night when my new pj showed up at the door. I have all the rolled panels done. But the only thing I accomplished spraying-wise was to mix paint and water for the proper consistency. Turned out to be 3 cups of VUPE and 2/3 cup of distilled water.

I have two coats done for the translucency experiments now. And since sprayed coats dry much faster than rolled coats, I hope to be done by noon!

**Richum** · **03-13-09, 12:54 PM**

Quote:

mechman wrote:

I kind of took a detour last night when my new pj showed up at the door. I have all the rolled panels done. But the only thing I accomplished spraying-wise was to mix paint and water for the proper consistency. Turned out to be 3 cups of VUPE and 2/3 cup of distilled water.

I have two coats done for the translucency experiments now. And since sprayed coats dry much faster than rolled coats, I hope to be done by noon!

mechman,

Please pardon my ignorance but, by what method will you determine the translucency of your samples?

That is one fantastic idea and should tell the tale about coating a reflective surface. I can't wait for the results!

**mechman** · **03-13-09, 05:41 PM**

Richum,

Via a one degree spot meter.

Kind of the same principle as reading gain but backwards.

All panels are finished and I'll let them cure until next week. Expect data next Thursday!

**mechman** · **03-14-09, 05:07 PM**

These are the mirror tiles I used:

They're 12X12" and supposed to be 3mm thick. My caliper measured them at 2.72mm though. I haven't measured the thickness of the sprayed mirrors yet.

**mechman** · **03-18-09, 10:59 PM**

I did get readings tonight from all of my mirror samples. I'm holding off on reporting anything until Harp can confirm what I found. The numbers are not what I expected at all.

My advice for now is that a mirror purchase is the equivalent of throwing money down the drain.

For the record, I saw no hot spotting on my 12" tiles. I'd guess this is due to their small size. I'm fairly certain that a larger mirror would show the hot spots. I may purchase a larger mirror in a few months just to test this out.

**Richum** · **03-18-09, 11:14 PM**

Quote:

mechman wrote:

I did get readings tonight from all of my mirror samples. I'm holding off on reporting anything until Harp can confirm what I found. The numbers are not what I expected at all.

My advice for now is that a mirror purchase is the equivalent of throwing money down the drain.

For the record, I saw no hot spotting on my 12" tiles. I'd guess this is due to their small size. I'm fairly certain that a larger mirror would show the hot spots. I may purchase a larger mirror in a few months just to test this out.

As I suspected. I saw no anecdotal evidence during my experiments that mirrors (reflective substrates) provided any benefit. To me my work indicated that all substrates coated with the same formula would produce the same or nearly the same results.

**mechman** · **03-19-09, 01:49 AM**

Quote:

Richum wrote:

As I suspected. I saw no anecdotal evidence during my experiments that mirrors (reflective substrates) provided any benefit. To me my work indicated that all substrates coated with the same formula would produce the same or nearly the same results.

Well let's say my initial observation agrees with you.

Right now, a pressed hardboard substrate yields matched results as a mirror.

There's more to look into though. This was an interesting shot of two sprayed mirror tiles. Left having one coat of rolled paint, right one coat of sprayed. Harp caught something I completely missed. Do you see it? That was with camera flash.

**Richum** · **03-19-09, 08:04 AM**

What do I see? The one on the left is lighter but the one on the right appears to have more detail when you look at the reflection where they meet in the middle.

I remember that the main proponent of mirrors was telling those who were spraying to do a what he called a light bulb test. Passing the light along the surface to inspect for uneven coating or thin areas based on the brightness of the bulb's reflection.

mechman if you haven't tried this already it might give an idea where you are as you lay down coats.

I wonder if anything other than a first surface mirror and a properly formulated thin membrane coating will ever produce any significant results.

**mechman** · **03-19-09, 10:06 AM**

I'll try the light bulb out today. Looking at the translucency tests I did (I'll be posting that today in that thread), spraying gives a more even coating than rolling does. So that confirms Richum's hunch.

Rolling gives you a thick coat quickly, but it's very uneven. I need to get more photos of that today as well. My initial photos turned out OK, but I forgot to take the plastic protective sheet off of the back side.

Anyways, with regards to that photo above, the interesting thing was the reflection. At first we thought it was coming from the mirrors. This morning I realized it was just a reflection off of the glossy laminate material used to hold the protractor in place.

Richum - have you ever tried spraying a larger mirror at all? Or just the 12X12 tiles like me? I'm a bit hesitant to post the data until Harp confirms what I've done. But suffice it to say that my reference panel of 1/8" hardboard - primed with Kilz2 (rolled) and sprayed with 6 coats of Valspar Ultra Prem Flat Enamel White - was as bright as the highest reading of any mirror tile. And I took measurements from every conceivable angle. I laid on the floor, I stood up, I hunched down, etc. I just could not find a bright spot.

And to be honest, I didn't think this would happen. I thought it would be brighter. But I also thought it would distort the image and hot spot.

**Richum** · **03-19-09, 04:11 PM**

[QUOTE=mechman;Richum - have you ever tried spraying a larger mirror at all? Or just the 12X12 tiles like me? [/QUOTE]

I have not tried spraying any thing near full size. I did roll a larger piece of first surface mirror salvaged from a projection tv a couple of years back. I can't remember enough about it to give details, except to say we were not impressed.

As I wrote previous, a reflective surface with just the "right" thickness of coating might work. However the coating would need to be precisely deposited and that would be difficult to do by hand on a large surface, none the less I am still considering breaking out the spray equipment and using my remaining Auto Air Aluminum to coat some fiberboard and hit it with a dust coat of Bermuda Beige thinned enough to spray.

The thought occurred to me that maybe it is a balance, not too shiny a substrate and not too thick a top coat. It seems to me that coating a mirror until it no longer hot spots makes for a coating that is too thick to be translucent. I think I will take that approach with AAA and BB, very thin layers testing between.

**Richum** · **03-20-09, 12:58 PM**

Today I shot a 24 x 48" piece of fiberboard, half with Auto Air Aluminum and half with Cream and Sugar. I then top coated the entire piece with Bermuda Beige.

On the half with AAA, I laid down two thin coats until it gave the appearance of being a Black Widow while over the C&S I shot thin coats until the C&S just disappeared as a color and it appeared as a light Bermuda Beige.

My impressions without any real cure time;

There is no hot spotting on AAA half and to the best of my memory it preforms the same or similar to Black Widow (I recently tossed my BW screen during spring cleaning). The other half is basically a Bermuda Beige screen as I expected it would be, I just wanted to have a comparison with a whiter base against the silver base.

After a day of drying time I will project on the sample again with it propped up against a large Cream and Sugar screen and report back. I do not hold out high hopes for this, but hey you never know.

**mechman** · **03-21-09, 10:46 AM**

Harp confirmed my findings last night - that a sprayed mirror tile offers no advantage to painted hardboard.

Data and conclusion posted in third post. I believe this thread, as well as the translucency thread, will live on for a while though. We'll continue to investigate mediums to add translucency to paint that actually work. Prof.'s been telling us about this since we've been here at the Shack!

**Richum** · **03-21-09, 04:35 PM**

Quote:

mechman wrote:

Harp confirmed my findings last night - that a sprayed mirror tile offers no advantage to painted hardboard.

Data and conclusion posted in third post. I believe this thread, as well as the translucency thread, will live on for a while though. We'll continue to investigate mediums to add translucency to paint that actually work. Prof.'s been telling us about this since we've been here at the Shack!

I sure hope the work continues, if I should stumble upon something I will post.

**mechman** · **03-21-09, 04:49 PM**

Quote:

Richum wrote:

I sure hope the work continues, if I should stumble upon something I will post.

The diy side of things is going to slow to a crawl the next couple of months for myself. I have a boat load of screen materials from Da-Lite, Elite, Vutec, Stewart, Beamax, Draper, and DNP to sort through and write up. After that I'd like to research this some more. And I've got the latest Silver Fire formula to putz with as well.

**Harpmaker** · **03-29-09, 11:37 PM**

An update on the continuing saga of painting mirrors.

While mech has shown (and I have verified at his request) that Valspar Ultra Premium Enamel by itself (and I assume other common house paints would be similar) will show no improvement over primed hardboard when painted on a mirror substrate, I wondered what would happen with a mix that had a large percentage of clear medium in it. I happened to have such a mix left over from doing testing into a possible BW mix to make a roll-up/retractable screen. This mix is 44.4% clear artist's medium, and while it is a long way from being transparent, it does show that a mix with enough translucency can work with a mirror. I'll speak more about this BW mix in the Flexible thread in the Developer's Forum.

For those that don't know, the wall I test my panels on is the same wall I paint my panels on. Sorry, nothing fancy here, just thought I would explain why there are a number of various gray/white areas on the wall.

All these photos are with the camera about 15 feet from the "screen". Screen brightness was about 14fL. Regular BW is on the left hardboard panel and BW-Flex is on a mirror on the right. 12" mirror tiles and matching hardboard panels were used.

Room light. Both panels look the same shade.

Camera flash. The mirror is showing gain.

PJ illumination - 90 degrees. Notice how much brighter the mirror is!

PJ illumination - 7.6 degrees from 90. Still pretty bright.

PJ illumination - 14.9 degrees from 90.

PJ illumination - 31 degrees from 90. At this point the panels are about the same apparent shade. This is a wide viewing cone! The equivalent of an 18 foot wide couch at 15 feet from the screen!

A contrast bar shot, but so few bars are visible it might not tell much.

I'm still kicking myself for forgetting to paint a primed hardboard panel when I did the mirror, but in these next photos I included the window shade I painted with the same BW-Flex mix with about the same number of coats of paint (maybe one more).

Room light. The shade is showing a bit of it's natural N9.5 white on the far left, but the bulk of it is BW-Flex. That puts the BW panel in the middle and the BW-Flex mirror on the right.

Camera flash.

Contrast bars. The shade ends just above the "255" in the bottom-left of the photo; the other panels are within the purple tape rectangle.

While it is possible to get a gain increase under the right circumstances by using a mirror as a substrate, it is doubtful that is it worth the cost and bother. Mirrors the size of most home theater screens are hard to find and quite expensive if you can find one. If one were going to spend that much money on a screen, commercial screens begin to look better and better.

**mechman** · **03-30-09, 11:39 AM**

And it appears that it actually 'robs Peter to pay Paul'. The whites improve and the blacks fade. My thoughts would be to go with a lighter mix and enjoy the wider viewing cone.

**Harpmaker** · **03-30-09, 01:34 PM**

Quote:

mechman wrote:

And it appears that it actually 'robs Peter to pay Paul'. The whites improve and the blacks fade. My thoughts would be to go with a lighter mix and enjoy the wider viewing cone.

Correct. The only possible advantage I see for painting mirrors might be in dealing with ambient light (a physically darker mix acts like a lighter one), but that is a big maybe.

**mechman** · **03-30-09, 06:54 PM**

And that one does really look like hot spotting to me.

**Harpmaker** · **03-30-09, 08:16 PM**

Quote:

mechman wrote:

And that one does really look like hot spotting to me.

Didn't see any on my end.

I made the mistake of having my PJ in focus for the white image; you can see my pixel grid because I'm zoomed in so much with the camera.

**Ericglo** · **04-17-09, 10:44 PM**

You guys might want to go and read some of my posts on this subject over at AVS.

Vutec made their UHG screen for years until discontinueing production a couple of years ago. It was a solid Torus screen with a very high gain. I per chance talked to Vutec's supplier of materials for this screen and it was mirror mylar with a translucent material laminated to it. I forgot what the hard back surface was. I believe that this is how most of the older screens were made for the front projection TVs of the early 80s like Sony. The gain helped give CRTs a very nice bright image. There was a guy in Tn who owned this screen with a Marquee 9500. He loved it and was able to reduce his contrast to save his tubes.

For the DIY arena, I tested Fusion with a regular mirror along with spraying mylar. A second surface mirror produced to blurry of an image. The mylar(first surface) can produce the high gain. I used my leather coatings and found that even a very little pigment would eliminate the translucency. I mean less than 1 percent. I did use a my dullest coating, which has an effect. Maybe a higher sheen with less dullers could take more pigment.
My thought was to maybe use barium sulfate to reduce the gain and give a more accurate or neutral screen. I was going to do a Torus with this, but gave up on the barium sulfate do to cost. I still may do a Torus, but with no pigment and ultra high gain.
For the digitals

, you can't really do a Torus. My other thought was to use a dark translucent coating to reduce the gain to around unity. The theory being that a darker color would give you the benefit of a dark gray screen and without losing gain. I played with it very little, but this would be the avenue that I would go down for mirrors with digital pjs.
I would give some pics, but I don't think I have enough posts. I joined this forum just for this thread, so don't give up. You just need to look at this in a different light (fusion).

**wbassett** · **04-18-09, 12:48 AM**

Hey Eric! Welcome to the Shack!

It's great to see old friends that have a lot of knowledge too!

**Richum** · **04-18-09, 07:07 AM**

Hello eric,

I do remember reading your posts over at avs and I am going to revisit those. What thread tile/subject should I search on?

I have looked at mylar but always understood that it is a pain to mount on a backing. I did run into a supplier's website where he shows plans for making a huge mirror with mylar film. The mirror is built using pvc pipe as a frame and is tensioned from the corners as I remember.

When your post count gets to the point where you can post those pictures you mentioned, please do.

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