914 Windshield inside OEM Glass Sticker logo?, Anyone making these OEM Windshield Mfg. Stickers Options

[TJB/914]

Looking for help if anyone makes these OEM Windshield Sticker's?
Are they different for every model year?
Many years ago while restoring my 914 I used a solvent to clean up the windshield glass & destroyed the letters. I would like one for my OEM original windshield (IMG:style_emoticons/default/pray.gif)
This is off as recent 1976 in a local shop for repairs in this photo.
Tom Michigan

[vitamin914]

@wonkipop
@JeffBowlsby


There is a historical meaning to various terms like toughened, tempered, float and plate.

I would say 99.99% of all windshield glass now made is from laminated sheets of annealed float glass. None of it is tempered or toughened. It may have at some point in history but the reason is rather obvious. Have you ever seen how tempered glass shatters into what looks like ice crystals? Imagine a stone hitting the windshield and instantly the glass turns into that? You suddenly wouldn't see anything in front of you.

The terms plate glass and float glass were used to describe the process of making glass... plate glass was typically drawn vertically out of a molten pool of glass. It would have a wavy pattern and it was ground and polished to make it flat. Float glass is made by molten glass flowing out onto molten tin ribbon and "floating" on it until it cooled. This was obviously a better glass. I can see there being differences in mechanical properties between float and plate glass and that may be the difference in some trademarks having float or plate designations. I don't know when thing like that happened in what years. Now the terms are interchangeable.

Trivia... what does PPG stand for? Many think it is Pittsburgh Paint and Glass - wrong. It actually was Pittsburgh Plate Glass. They were the first company to successfully operate a commercial plate glass process.


Annealed, tempered, toughened.

Windshields are made from annealed glass. Two pieces of glass are cut with the inner piece being a bit smaller so when they bend, the edges line up to be square. The flat glass is dusted with a material so the two pieces do not stick together when being bent.

The flat glass is placed on "bending irons" which are typically made of stainless steel with pivoting weighted wings. The bending irons support the glass around the periphery and as the glass travels through the lehr (bending furnace) it softens, sags and bends into shape by gravity. It takes a lot of skill with the right heating profiles to get the glass into the right shape. After slow cooling the layers are separated and the PVB vinyl gets inserted then heated with a vacuum or nipper rollers to squeeze out air. The final process it is put into a huge autoclave to be heated and pressurized. That squeezes the glass to the vinyl gets the air out and it goes from milky to clear.

Tempered glass is similar but different. Glass is cut, machined for size and to give a rounded edge and if needed, drill holes for hardware. The glass goes through a furnace on ceramic rollers to a bending station where it gets picked up (with a vacuum) and dropped onto a bending form. Then it is immediately basted with compressed air from oscillating nozzles that cool the glass rapidly tempering it. This induces huge stresses. The outsides are in compression the core is in tension. It gives the glass lots of physical strength but that is not where the safety part comes from. If the compressive layer is comprised (by an impact) the stress becomes unbalanced at the the entire piece shatters into tiny fragments. None of these fragments are large enough to make a knifelike shard that will cut you deeply. This is the safety part. Strong (I have stood on a curved side window without it breaking) cheap and safe. Sometimes you can see the nozzle stress patterns in tempered back windows of cars if you are wearing polarized sunglasses.

Most tempered glass is now made horizontally on rollers.
Earlier tempered glass went through the furnace hung vertically from tongs. The glass was then pressed from the sides before being tempered. It has very characteristic tong marks or dimples pushed into the glass surface near one edge. I think I saw these on the side glass of our 914s?


Tempered glass has specifications for how it breaks. There is a maximum weight for the largest shattered piece. Euro standards have smaller size fragments and are harder to make. I remember when when we had to make a Euro spec window for a customer and the process could not cool the glass fast enough in the summer (hot ambient air). The plant manager went baillistic saying what am I supposed to tell the customer that we can't make their glass in the summer? Well... yeah... it's physics. Thinner glass is harder to properly temper than thicker glass too.

Toughened glass is tempered glass but not to the same level. The shards will be bigger.

One of my jobs as a young engineer was to test glass samples in the lab by dropping metal darts and huge ball bearings from various heights onto the glass. We would log the test results and have to send additional samples out to Underwriters Labs or Canadian Standards Association for independent certification. I just did the testing not the submissions. This is where the M numbers were used. The M number would be the certification for that particular type of glass, thickness, lamination / temper etc. It is very possible that the M number had to go to the DOT for registration - but I don't know that for a fact. We also did light transmission and abrasion testing on the glass too. All of this was recorded for each M number.

Although there is a lot of science in making glass, there is also a lot art in the process too. It takes a lot more for everything to come together than we sometimes imagine.

You guys have done some amazing research on the trademarks or "bugs" as some call them. Bravo!

Don't get too hung up on the way things are presented in the trademarks. There were no hard and fast rules. It had to meet regulations for minimum information but beyond that it was up to the glass company how they presented it. Sometimes the auto maker wanted specific things (like logos or bar codes) but they left the rest to us. We had a standardized trademark catalog but often had to make minor changes. Obviously, aftermarket replacement glass was much less strict than OEM (that required the car maker to approve).