A wise person once said "The enemy of good is better."

This applies in your case in that if you clear the back of the glass you will most probably compromise an appearance aspect to secure the existing paint. That compromise will be at the score and credit windows either to block them out or if you float a heavy coat over them. If you block them you will see the edge of the clear and possibly damage the paint at those locations. If you float a heavy coat you may have some distortion at the score windows.

My advice is to leave it alone as long as it resides in a temperature/humidity controlled environment. If that is the case it won't get any worse.

Simply measure the windows, cut out some cardboard of the appropriate size, put nickels on the pieces of cardboard so they don't get blown around by spraying the triple thick.

The the triple thick still covers a bit of the score window, a razor blade with a steady hand will take care of it.

https://pinside.com/pinball/forum/topic/concern-about-using-triple-thick-on-backglass

Bubbling is a tough thing and in my experience, back glasses prone to it will continue to bubble. Generally can't be repaired as good as actually peeling paint. However, if it was mine, I would not hesitate to clear coat it. Had a Rolling Stones (Bally) that bubbled badly on the ride home when I purchased it. Did not even attempt to try and repair it....but I believe that clear coat can restrict further bubbling.

My method of clear coating is much simpler than most on here, but I also believe it is very quick and effective. Lay the glass flat (level), shake up two cans of Triple Thick and spray both cans at once. This allows you to get a very wet coat down in just one shot...and done. I spray right over the score glasses as well and very rarely are they less than acceptable.

Also consider LED's for the back glass lighting...less heat. On my Rolling Stones, the bubbling occurred where the lighting was the most intense. Note...I did find a beautiful NOS back glass for my Rolling Stones... So now I have a piece of nice, but bubbled, artwork.

Mike, I have two glass-related questions and would love your advice. First, I have a gorgeous (near perfect) back-glass on my 1977 Bronco. My games are in an arcade area I've created in an insulated three-car garage and I do keep the games and heads covered when I'm not using them (at night, etc.). I do have a heater in the arcade area for wintertime, and thankfully we do avoid most of the weather extremes (rarely very hot, rarely super-cold) here in the Seattle area, but because it's a garage the doors are open alot so it is exposed to the ambient humidity. In that environment would you recommend I spray my back-glasses?

Second, I have bought a repro back-glass for my Target Alpha that should be arriving later this week. When swapping out a back-glass, is it generally recommended to take the head off the game and do it on a carpet on the floor? Fine doing it either way (on the game or off) but wasn't sure if conventional wisdom is to take the head off because it's easier to maneuver the glass that way.

Thanks!

Agree...overspray can be easily removed with a nice clean razor blade.

I don't get concerned about humidity here in the Kansas City area and have had no issues. We aren't tropical. I don't leave glasses in the garage in the winter here, even though my garage does not get down to freezing, even though it gets to the 30's some times. Freeze and direct moisture accumulation are your enemies. As long as the garage and outdoor are similar temps and humidity you won't get condensation issues.

Leave the head on the game. The way you remove a glass on a Gottlieb of this era is as follows:
1. Remove rear door.
2. Tilt out head relay board and allow to rest on stops.
3. Holding sides of backglass, pull bottom edge of glass back until is slips down into slot in bottom of head.
4. Arch top edge of glass back and rotate whole glass out of game staying below latch arm and above head relay board.

Installation is the reverse of removal.

Be patient. You can scratch the art if you drag it hard along the head relay board.

On a Gottlieb glass of this era I disagree. The windows do not have square corners, instead have rounded corners, and can't be cleaned up easily with a straight razor blade. I've never gotten a good clear on a Gottlieb glass of this era where I don't trade the improvement in sealing the glass for a cosmetic anomaly due to the rounded corners.

Then just use a corner of the blade.

I just use pieces of 1/4" thick wood cut to 1/32" larger than the area you are masking off. Then I mask off the corners of the wood that will sit face down with painter's tape, so that any pores or imperfections in the wood don't allow overspray. I've never had an overspray issue doing this. For rounded corners or oval openings, cut a diamond to 1/16" larger than the largest diameter of the opening and use your grinder wheel to round the edges. If it's not perfect, don't worry about it. You won't notice a few small spots of the painted parts of the glass are bare unless you really scrutinize the BG with a magnifying glass from behind.

If you've never cleared a BG, practice on some old PF glass. It's surprisingly easy to go overboard when clearing. It only takes 2 thin coats to seal up a BG. I'd also never suggest using clear on a severely cracked up backglass if you're not already skilled with spray paint. It takes very little to blow off pieces of the paint if they are flaking off. The pinrepair site's idea of using plastic wrap and a lot of patience is needed in those instances.

If it's just one spot, you can just clear that spot. You can also move back the light sockets/put in cooler bulbs/remove bulbs from the area that is getting affected.

Not that bad is likely to get worse... even in your house. I advocate for triple thick with masking over score windows. Careful with the edges, but can be done fairly easily.

I guess you could do only a part but that may actually cause problems as it would change the expansion/contraction properties of a limited portion of the paint and might induce trouble.

I would spray it and lock it down.

Its worth noting that almost nobody can actually fix damage on a painted back glass- its beyond difficult to get the colors right with back illumination. Lock it in, you have very few real world options to repair it. If someone reading this knows of a fee based service that REPAIRS damage, please link to it (cost might be interesting if known).

(BGrestoro, so far as I know, does not offer repair services, they manufacturer new repro's which look nearly identical).

I would triple-thick your glass IMHO only because you say "it's starting to bubble". That tells me it has de-laminated and will probably get worse. A scratch or nick in the paint doesn't qualify for sealing but bubbling does. By sealing the glass you will prevent any future damage if done correctly.

Make sure you use Triple Thick Crystal Clear Glaze #0500. I cut my card stock to about 1/32" in from the painted edge of the score windows and weight them down with nuts, washers, anything heavy and cheap. Don't let your cutouts extend into the painted area of the score reel window. This is where damage can occur when you lift the cutouts. Humidity is critical in sealing a glass so make sure the humidity is low enough when you do the job. Temperature in the wintertime is critical too but not this time of year. Spray one heavy coat and allow to dry 24 hours and then turn the glass and spray a lighter coat in reverse direction. Reverse again if you do a light 3rd coat.

As someone has already mentioned, take great care in removing your cutouts over the score reels after the TT has dried. I use a razor blade and carefully lift a corner of the cutout. Also, work like a surgeon when removing any residue on the clear glass - especially the corners.

Good luck whatever you do.

I'm going out to seal a Pioneer glass right now...........

Good discussion. I'm wondering what to do with my near mint Atlantis back glass and also my soon to arrive new Space Odyssey repro. To TT as preventative measure or not?

I'm still uncertain what humidity and temp exposures are "bad" for pins and EM back glass....we live in northern BC and we burn a wood stove a lot in winter, just so happens this is the same room as our pins, and I know our relative humidity is dry in summer and dry in winter....hey it is a dry cold! we do have to run a humidifier in winter in very cold temps as everything just gets dry even the snow!

so obviously our pin room won't freeze but I do wonder if I should be taking some kind of steps to minimize risk of flaking back glass....which is why I do have 2 cans of TT on my shelf.

Is low humidity also bad for bg, or just high humidity?
I think freezing temps are not be a good thing,and also big temp swings in very short period. right?
If both bgs are flake free then should I just leave them alone? Thanks for your advice!

Low humidity = good
High Humidity = bad

Extreme temperature changes from hot to cold or cold to hot = the worst thing you can do
Gradual cooling to 40 deg F = ok
Cold under 40 deg F = bad

If both bg's are flake-free with no visible bubbling/de-lamination you're right I would leave them alone.

JMHO....

Ditto.

I have "heard" that TT on a good glass that doesn't need it actually raises potential for problems. If your glass is good there's no reason it'll go bad spontaneously in a home setting...unless it has a bunch of temp changes etc. I would only use if you have flaking/bubbling.

This is great information and I've saved it. I want to TT my backglasses to protect them but how do you get a United woodrail backglass out of the backbox? It doesn't have the lever that holds the board with workings in like the wedgeheads do.

You might want to start another thread and ask that question hoping a United owner sees it. Also, search old threads here and on rec.games.pinball using the keywords United backglass.

I was hoping you or a United woodrail owner would know. Will do what you suggested and update here.

I've never owned a United - maybe someday.......

There's something about United's backglass art and the games themselves that I like. Maybe someday I'll get a second one to put next to the one I have.

It depends on the era of the game, but one of the 4 molding pieces should have screws. Unscrew those, remove that piece of molding, and the backglass slides out. It's usually the left or right side molding piece.

It's a 1949 United "UTAH" pinball machine and I found two screws on each side of the backbox but I want to be careful with this backglass. You don't see this game every day, it would be hard to find a replacement.

20150604_214647.jpg

There was also a suggestion that the strip on top of the backbox needs to be removed for the backglass to come out in this thread.

https://pinside.com/pinball/forum/topic/united-mfg-woodrail-backglass-removal#post-2492818

20150604_214716.jpg