Anyone know of a paint that will adhere well to glass? This is high-end “starfire” glass, not cheap window panes. And it’s an interior application… going somewhere inside Portland International Airport.
I’ve just been notified of a job which involves making the backside of a series of glass panels white, presumably for it’s reflective value since there will be screen printed text on the front side. I checked into spraying a protective clearcoat over frosted glass, to prevent fingerprints, last year sometime and the feedback I got as far as automotive paints was that nobody could guarantee adhesion. Fortunately this job involves backpainting and it’s not in a touch zone. But I’m still concerned about adhesion.
One possible option that I’m thinking of, and which is partly why I’m posting this here, is custom-colored shellac. I know from past conversations with folks who paint sales slogans and stuff like that on the windows of stores and fastfood joints that shellac is their favored medium and that it has to be scraped off with a razor blade – implying at least decent adhesion. So I’m wondering if anyone here has custom colored shellac with pigments and if so, what did you use? I’m told thus far only that it’s to be white. But knowing designers I’m guessing they’re going to want some sort of custom white.
Oh… and if it helps (our conservative friends will probably like this), the subject of the display is Oregon’s last Republican Governor (Vic Atiyah), who is likely to retain that distinction for the foreseeable future, and his trail blazing efforts as far as international commerce trade with Oregon – which is why it’s going into PDX.
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Won't standard Zinzer or B.I.N. Primer stick to glass? I believe it generally comes already tinted white and is also tint-able. It can be brushed or sprayed and I think it's actually a shellac base? Worth looking into I think.
Yes, I'd thought of that. But what is it tintable with?
That, I'm afraid I don't know however it may be as simple as contacting the paint dept of your local home center and asking them if, and with what, they can tint that particular primer. Having worked in a home center when I was a wee lad we had a variety of different tints that we used to tint the variety of bases we offered. Conversely perhaps someone will answer your question with personal experience here or on the ask the experts forum. If the piece is to be completely painted (solid color) and is in a non-touch zone is it also in a non-visble zone in the back? If so, I would think you could use some sort of sandwich technique using a wide variety of materials to get a solid white background, if not simply the same vinyl they'll be using on the front?
You bring up the other option being discussed internally here - vinyl. Our pencil-pusher is concerned that we (we have an in-house graphics dept.) won't be able to get that much vinyl on that large a surface area without any bubbles (which would be very visible from the front) and/or that it could bubble later and we'd not be able to fix it. So everyone is hoping that I can come up with a paint solution. Even so, the plan here is apparently to do two samples, one with paint and one with vinyl, and see what the outside designer says. Personally... I'd rather they go with the vinyl because I know it'll adhere well. In fact that was my first question when first approached with the job - why not use vinyl? LOL I actually ask that question a lot more often than I wish I had to. But alas that's the nature of this business I'm in. Designers dream stuff up and we have to try to turn it into reality. Fun, but frequently very frustrating too.
Applying a sheet surface would actually be doable, the concern I have is the side being viewed is the adhesive side. The adhesive may not be white, or truly transparent enough to allow the color to show through or be UV stable. Discoloration may occur. The adhesive side is often not glossy, or the same sheen as the face side.
If you have to apply a back ground after instillation your options are.......
Imron would have to applied in a spray booth. I suspect anything with a smell would be less favored by airport management or prohibited.
The aluminum sheet in roll form or stretched fabric....... over a 3 sided frame and secure it to the RT. and Left verticals and the top horizontal.
Silk screen ink the same as the front,.?!
Don't forget to check the products under the same lights, you know how that changes things.
Ron
Yeah, the adhesive side of a sheet good would likely be a problem. It would not only have to be a transparent adhesive but it would also have to have perfect 100% adhesion because you'd be able to see any area that hadn't adhered since the viewer would be seeing the sheet good through the adhesive. I think that vinyl is probably the best of those types of options.
I have a massive spray booth at my disposal here at work, so that's not a problem. And there are several water-borne versions of Imron which probably wouldn't pose a smell problem. But I'm not sure that Imron would adhere any better or even as good as shellac, which is why I'm still leaning that direction.
I have thought of trying to thin down and spray a screen ink. I'm not sure that would work, though. From what I remember, and it's been a few years, one of the main tricks to getting screen inks to adhere well to a difficult surface is to use a retarding solvent which apparently gives it longer to bite into what little there is to bite into. I'd have dust problems if I tried to replicate that with a sprayable formula.
I'm thinking that shellac is the way to go here. Not sure what kind of pigments would be ideal, but I can do some phone work and find out.
Thank you very much for the thoughful and thought provoking feedback!
Check your craft store--Michael's or Hobby Lobby. They have glass paint.Gretchen
Kevin, permanent glass coating (stained glass) are painted and fired over 1200F. You may want to look for a technical glass organization, Glass Digest or some other non hobby group, glass engineers. Speak with the folks who manufacture the "starfire"
There may well be an acid based finish that will etch the surface and deliver color, I don't know.
But I'm still concerned about adhesion and color consistency.
Having some background in glass, I have my reservations as to the nature of your quest. Permanence in glass requires etching, sandblasting, or painting and firing.
Do you have the technical sheet on "starfire" What are they screening with?
I would truly like to have an answer for you but if you said a project that will be replaced in 2-3 years, sure you can use an automotive finish, Dupont Imron sticks to anything, its very expensive.
On second thought you can't sand blast it, I'm sure it tempered, being in a public place.
Aluminum gutter suppliers may have prepainted aluminum in roll form. That's my best thought, Paint the panels any color, texture, sheen, and attach with some small aluminum. tabs and very short pop rivets or screws.
I hope I helped in some way.
Ron
First of all, thank you for the very thoughtful reply. It's exactly what I was looking for, short of a surefire paint that would meet all of my criteria and be easy to apply.
Well I'm concerned a bit about color consistency. Although with backpainting it's a lot easier to get consistent color because you just need to get enough coverage with good enough atomization to give a uniform opacity of the right color... not unlike how silvering the backside of glass makes a mirror.
My primary concern is adhesion. While I rather suspect that this display will be replaced in two or three years as you suggest, and that means that I don't have to have perfect adhesion, I'm concerned about it getting beyond the install. Once everything is installed and in place it should be fine for the life of the exhibit. But a scratch through on something that's backpainted would be extremely difficult to repair.
I don't know what they're screening it with. However I have some slight background in screen printing and know that certain inks will adhere exceptionally well to surfaces that are problematic for paints unless treated with some sort of etching primer.
I had thought of suggesting that the backside be sandblasted first, which should at least aid in adhesion. But I'm pretty sure that the designer would shoot that idea down for visual reasons even if it were an option with this glass.
What I've been told about this Starfire glass is that it's supposed to have superior optical clarity. Other than that I'm assuming that it should behave like any other type of glass as far as paint adhesion is concerned.
Unfortunately I don't think the aluminum idea is workable here for the same reason as blasting isn't - visual considerations. The way this project is designed... there is a series of I think it's 8 to 10 glass panels and they will be siliconed together on the edges so that it's one long glass display, captured on the top, bottom and both ends. I think it's going into some kind of alcove. So what they're wanting is just a white background that won't intrude visually in any way.
My hunch is that shellac is probably my best option. It's not as tough as automotive or industrial paint, such as Imron which I know is super durable, and may be more problematic during the install, but I think it'll have better adhesion. I think...
Still open to ideas, though. I suspect there is no good option here... Just a lesser of two or more evils option.
This is a commercial job supposedly, so whoever is in charge, the general contractor, designer, or architect should be specifying the paint and application process in writing.
Also this sounds badly planned, going "somewhere" in the airport and it may only be temporary but you're not sure. This should be someone elses decision and headache if it fails.
John White, Shop Manager, Fine Woodworking Magazine
Well, this job is commercial in the sense that there's a contract and all that involved. Sometimes we're working for the ultimate client, sometimes for a design firm and once a while we're working for a general contractor. Sometimes the paint and application process are specified, but usually it's not. Particularly on jobs like this one where there simply is no established paint or process for exactly what they want us to do. It's not at all uncommon for a potential client to solicit a bid for a project which is only loosely define. They tell us what they want and we tell them what it will take to make it happen and how much we'd charge for our services. The vast majority of what we do is custom, one-off stuff. The remainder is mostly just replicating something that started out as a custom, one-off thing designed and fabricated by us.
It might help to point out that my employer does both fabrication and design. We have full design, graphics, warehouse and fabrication (including both a full metal fab shop and my paint shop) facilities in-house. So often our in-house designers are involved somewhere in the scheme or an outside designer/architect has come up with the grand scheme but we do the design details for the part that's subbed to us.
As for this project, I've seen the computer renderings that are part of our bid estimate. Where in the airport it goes really isn't relevant to me, thus I wasn't told nor did I think to ask. In any case, our warrenty for what we produce typically covers the first year after installation. The rest is all details for which others collect their own paychecks for knowing all the details of. I'm only concerned with the part that I have to work on - backpainting the glass white and with acceptable adhesion. And there I think I've finally struck gold.
The owner of one of my paint suppliers and I huddled this morning and it turns out that the front windows in his facility are backpainted with Pratt & Lambert SuPrime 1 and it's been on there for 20 years and still holding on just great. It's also tintable, meaning that he can custom tint it for me if it ends up being the case that a specific white is necessary to match to. He actually first suggested tinted shellac. But after conferring with Zinsser and doing some trials of his own he found that he can't get a crisp bright white using shellac. So that's where the P&L primer came in. It is a brighter, crisper white to begin with and is fully tintable too.
Edited 5/4/2007 10:04 pm by Kevin
Thanks for sharing the soultion, please let us know how it turns out in the end as I am curious. Also, in your coversation about tinting Zinzer, even though it was decided that the white wasn't right, did you find out exactly what it can be tinted with?
Oh man... I knew I should have paid better attention. He mentioned two colorant lines that he could use and I honestly wasn't paying attention. I'll email my work computer with a reminder to call him up and find out so I can post it here.
Actually you might find this part, which I did pay attention to, interesting. When I first talked with him we discussed two approaches with shellac. One was to use the BIN shellac primer because it comes already with white in it. The other was to use Seal Coat and tint it white. The BIN primer is kind of a muddy white so he decided that he wanted to know for his own edification just how Seal Coat would look when tinted white. Surprisingly he was unable to get it crisply white or even as white as the BIN primer.
The person who is screen printing text on the front must have something that adheres to glass. Why not ask the screen printers if they have something that could be used to make the back white--perhaps they could do it for you.
--Whit
Good idea, Whit. I had thought of that. But I think there are two primary stumbling blocks. 1. it would be prohibitively expensive to screen the backside and I'm not sure the couple of silk screeners in the area who are capable of screening something that large would find it feasable even if it weren't expensive. And 2., as we know from working with finish materials like lacquers and varnishes, over-reducing them too much messes with their ability to form a cohesive film with the advertised properties and I doubt that thinning screen ink enough to make it sprayable would yield a material which would adhere the same as it does without thinning.
If the SuPrime 1 primer works then it will be a significantly cheaper way of meeting the job requirements than any of the other options that have been suggested. I'll be painting a small sample piece early next week. If it doesn't work then I'll be revisiting the other suggestions.
What about laminated glass with a solid white vinyl between the laminates? You probably couln't get a custom color but it would certainly be durable and consistent. Call a glass contractor to see what they would do.
Edited 5/6/2007 8:47 am ET by Joby
Interesting suggestion. I'll keep it in mind in case the backpainting is rejected.
Kevin, how big are the panels?
Some of the mylar films used for window tinting, are produced by companies that also produce white mylar plotter paper.
If the sizes are right you might be able to get a white window tint, and squeegee it on over a film of slightly soapy water, just like the glass tinters do.
The best option from my stand point, but I'm not sure the artist would go for it, would be to abandon the glass, and use a white sheet plastic material. (Corian, or and Acrylic come to mind). It would be white, stay white, and is strong in it's own right. It would not have the same visual effect as a back painted glass pane, but would provide a high gloss white background for the graphics.
On further thought; I would abandon the glass all together if they insist on a clear panel with a back painted surface, and go with a clear acrylic like "Lexan". There are grades that are optically pure enough to make high quality low distortion/absorption lenses, so I can't think of a reason it wouldn't work in the application.
By the way, "Starfire Clear Glass is a lead free, low iron product that represents the very best in glass trophies although not clear enough to be called 'crystal'. A slight blue tint is evident in the most-clear product."
I'll look into the mylar idea. It might work. I'm not positive about the size of each pane but I believe they are roughly 4'x8'.
My understanding is that the Starfire glass is not negotiable. We have experience backpainting plexiglass and that would definitely be my preference.
Thanks for the suggestions!
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