Part one is located here.
Work on the Black Widow paint project has taken up a considerable amount of my time as of late. And my keen interest in 'taming' the 3:1 mixtures has inevitably led me back to clear coats. Through many trips to home improvement stores I have always taken note of clears they stock. Home Depot stocks Behr 780 Matte Polyurethane and then the various Minwax products. Lowe's stocks Olympic, Valspar, Minwax, some Varathane, and other miscellaneous products. I could not find the American Traditions products described elsewhere in either of the stores close to me other than a clear gloss. All of the Varathanes at Lowe's are of the floor coating variety and only sold by the gallon for the cost of ~ $50. I mention this because as I was nearing the end of testing, benven mentioned that he used Varathane exterior polyurethane in his CGiv formula. While I haven't yet completed my search - I have a couple of Home Depots to check yet - I will keep looking and add an addendum when found.
So this brings us to an interesting point to consider right from the start. Exterior poly vs. interior poly. Exterior poly is used mainly as it has better UV resistance. That UV resistance will help in the long run from your screen shifting colors. Interior polyurethanes are less UV resistant than their exterior brethren. So what does that mean? UV stands for UltraViolet light. This light is produced naturally by our sun. It is also produced from black lights, mercury lights, and fluorescent lights. If you don't have any of these lights in your theater I wouldn't worry about using an interior grade poly. As to the sun, most windows will block a lot of the UV radiation from the sun.
If your theater is like mine and the sun never hits your screen and yet you have a bit of ambient light, you can be safe using an interior polyurethane.
The other question is to the quality and opacity of the polyurethane. Behr 780 has been used for quite some time as it is the only matte polyurethane available that I'm aware of. I have two rolled coats of Behr 780 on my Wilsonart Fashion Grey screen to eliminate the hot spots. There are spectro numbers on both poly coated and non poly coated Fashion Grey laminates in the Master Screen Data Index. The one thing that a lot of people have noticed however, is that it tends to soften the image very slightly and if it's rolled on thick it yellows as it dries. This is even in a non UV environment. So where do we go from there?
On one of my many trips to Lowe's I noticed a Valspar Clear Protector. They come in gloss, satin, and flat finishes. They are located, as the Behr 780 at Home Depot is, by the faux finishes and are intended to be used as a protector for faux finishes. One thing they did not have was a matte finish, but that's easily remedied by mixing equal portions of both satin and flat.
The bulk of this investigation will focus on the Valspar Clear's (VCP) and flat/satin combinations.
This next graph shows how much of a change there was in each particular color on the Winter Mist panel.
mech
Work on the Black Widow paint project has taken up a considerable amount of my time as of late. And my keen interest in 'taming' the 3:1 mixtures has inevitably led me back to clear coats. Through many trips to home improvement stores I have always taken note of clears they stock. Home Depot stocks Behr 780 Matte Polyurethane and then the various Minwax products. Lowe's stocks Olympic, Valspar, Minwax, some Varathane, and other miscellaneous products. I could not find the American Traditions products described elsewhere in either of the stores close to me other than a clear gloss. All of the Varathanes at Lowe's are of the floor coating variety and only sold by the gallon for the cost of ~ $50. I mention this because as I was nearing the end of testing, benven mentioned that he used Varathane exterior polyurethane in his CGiv formula. While I haven't yet completed my search - I have a couple of Home Depots to check yet - I will keep looking and add an addendum when found.
So this brings us to an interesting point to consider right from the start. Exterior poly vs. interior poly. Exterior poly is used mainly as it has better UV resistance. That UV resistance will help in the long run from your screen shifting colors. Interior polyurethanes are less UV resistant than their exterior brethren. So what does that mean? UV stands for UltraViolet light. This light is produced naturally by our sun. It is also produced from black lights, mercury lights, and fluorescent lights. If you don't have any of these lights in your theater I wouldn't worry about using an interior grade poly. As to the sun, most windows will block a lot of the UV radiation from the sun.
[PIE]Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm. Source - Wikipedia[/PIE]
If your theater is like mine and the sun never hits your screen and yet you have a bit of ambient light, you can be safe using an interior polyurethane.
The other question is to the quality and opacity of the polyurethane. Behr 780 has been used for quite some time as it is the only matte polyurethane available that I'm aware of. I have two rolled coats of Behr 780 on my Wilsonart Fashion Grey screen to eliminate the hot spots. There are spectro numbers on both poly coated and non poly coated Fashion Grey laminates in the Master Screen Data Index. The one thing that a lot of people have noticed however, is that it tends to soften the image very slightly and if it's rolled on thick it yellows as it dries. This is even in a non UV environment. So where do we go from there?
On one of my many trips to Lowe's I noticed a Valspar Clear Protector. They come in gloss, satin, and flat finishes. They are located, as the Behr 780 at Home Depot is, by the faux finishes and are intended to be used as a protector for faux finishes. One thing they did not have was a matte finish, but that's easily remedied by mixing equal portions of both satin and flat.
The bulk of this investigation will focus on the Valspar Clear's (VCP) and flat/satin combinations.
This next graph shows how much of a change there was in each particular color on the Winter Mist panel.
mech