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BW and Dark Spots

2783 Views 17 Replies 4 Participants Last post by  wbassett
Hey guys Ive been posting in here lately about getting my screen sprayed with BW...Well it's finally done!!! I'm very please with it but I have a couple concernes.....
1. there is a "texture" to the surface that was painted?? is this normal??? it's not huge like a topographical map or anything...but there is a "grain" like texture to it....like a real course sandpaper....

2. there are two distinct "dark spots" on the surface of the screen about the size of your hand... I asssume that either the BW layed down a bit thicker in these areas OR it layed down differently...My question is this....Can I go back with some fine girt sandpaper to try and take these areas down a bit and make it more uniform??? is this something that you guys have experience with?? is it advisable to go back over the entire surface area (not just the dark spots) to smooth out the texture that I was refering to in question 1???

Thanks in advance....and thanks to everyone for guidance in making this happen......Riff :bigsmile:
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1. In my experience, no, the surface should NOT look like really course sandpaper (like 36 grit). At it's roughest, I would guess maybe 120 grit. In normal, or even bright, room light there should be no apparent texture an arms length away from the screen; unless you're talking about a kind of granularity caused by the reflections off the aluminum flakes on the surface.

I can send you a small sample to compare your screen to if you would like. Just PM me an address.

2. Sorry to make you repeat yourself, but what kind of substrate are you using again? If it was primed, was the primer sprayed on? Was Kilz2 used? Sorry again - I should remember this data, but I don't. I'm gettin' old...

How much did your friend have to dilute the BW?

I just thought of something... you are using the HE558 5:1 mix right? When I sprayed my panels using HE558 mixes I found that the screen would tend to "smudge" if it was handled with bare hands even weeks after it "dried". Are the dark areas you refer to places when the screen could have been handled? This wasn't a problem when these mixes were rolled.

No, do NOT sand the screen! While I have never tried that, I think it would do more harm than good. My advice would be to apply another coat of BW. After it is dry, only handle it while wearing latex or nitrile gloves. The current theory is that oils from the skin somehow react with the asphalt in the HE558. My humblest apologies for not mentioning this before. I think the info is in the BW thread somewhere, but that is no excuse.
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When I sprayed my panels it was around 60 degrees F and medium humidity and my coats usually dried to the touch in about 10 minutes, but this depends greatly on the equipment used and how thick the paint can be applied before running. The higher the humidity the longer it will take the coat to dry; higher temps would help, but the atmosphere must be able to take up the water from the paint.

I have never painted BOC, and the more I learn about BOC the more problems I see painting it. It is doable with most BOC's, but there is a HUGE difference in what is being called BOC!

I ordered two different type of BOC from JoAnn Fabric and they are two VERY different fabrics. One is totally opaque to light (I've posted photos and specto data on it elsewhere) and the other looks like a bedsheet! It's very translucent and looks almost like a gauze! I have no idea how it could be used to block light.

Is your BOC coated on one side and uncoated on the other? Which side did you have painted? Again, sorry for my bad memory.

At this point, I'm wondering if the "dark spots" (caused by differences in screen texture) weren't in the fabric to start with, they would be hard to see on a white fabric unless a bright light was held at an oblique angle and texture differences looked for.

The other possibility is that the Kilz2 had to be thinned so much that the water reacted with the BOC in some areas differently than others. I'm saying this because the sprayer said that the first coat of BW had the spots, therefore it can't be smudging.

You're not being a pain Riff, not at all. I really hate it when someone has this much trouble getting a screen done.

As for the paint being rough, it can't really be called that unless comparing it to a glass-smooth surface. I did a test today (photo below) and you really can't use sandpaper grits to compare screen surfaces. I was wrong to compare BW HE558 to 120 grit, as you can see from the photo. To make long short, BW is not the cause of the texture on your screen; I sincerely think it's the BOC itself, or it's reaction to being painted with the primer.

In the macro photo below, the total width of the image is about 3/4 inch. The cream-colored material on the left is 60 grit sandpaper, the dark rust-colored material on the right is 120 grit sandpaper, the gray area is BW Winter Mist/HE558 5:1. Lighting was overhead fluorescents and a bright L.E.D. flashlight at a low angle from the top of the picture. Only the bottom area of the photo is in focus, but the grain-size of the sandpaper and BW can be seen. The aluminum flakes in the BW are very apparent, and in the area in focus, little black grains of the asphalt can be seen. This is a VERY close-up photo folks. :bigsmile:

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Is there any way you could post some photos of the spots? That might help a lot.

If they are caused by differing thicknesses of BW then the guy that sprayed the screen is at fault. I wonder if they could be areas where the paint sagged a little?

I can't help but think that sanding a BW HE558 screen would be a recipe for disaster, but it sounds like you have little to lose. Even if the BW is dry, it won't be cured for months (in my experience). I'll sand a portion of a test panel and get back to you with the results.

Again, sorry for making you repost info I'm sure you've given before; but what size is your screen horizontally and vertically? Was it mounted on it's frame when it was sprayed?

Dark spots aside, how do you like the screen image?
I'm working on some pictures now...I can take them...just no idea how to post them......
I would suggest uploading them to imageshack full-size and full resolution. Post a link here by just copying the link imageshack gives you that says it's to be used for forums and pasting it in your post here. No image will show in the post (unless you use the thumbnail option at imageshack), but we can then see the full-size image of the dark spots.

For hosting photos that are to be shown in posts, I much prefer to use photobucket; but you have to register there, you don't have to register at imageshack.


Sorry for taking so long to get back to you about sanding Riff. It's a super-busy weekend for me!

I sanded one end of the off-cut from my BW WM/HE558 5:1 panel (about 1 inch wide and 12 inches long) with a 220 grit sanding sponge and I was quite surprised. You might just get away with it.

Smudging was not a problem, but this piece of screen is cured as well as dried.

I won't have time to do any more testing before next week. This is very preliminary, but right now I would not recommend using any grit finer than 220, and there are indications that 150 or even 120 grit may be better. I'll know more next week.
OK, I just tried some 150 grit sandpaper on the BW WM/HE558 strip and I can't recommend it. It cuts too fast and leaves too rough a finish. Still no smudging, but it seems to be possible to sand enough so that aluminum flakes are less apparent. HE558 is a leafing aluminum product (the aluminum flakes try to float to the top of the paint before it dries).

If you have to sand, which is still NOT RECOMMENDED, do so lightly with 220 grit paper. Take your time and try to get an even appearance to the screen.
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