glas insert repair

[paelzermaen]

I wish I had a Matchbox window to test it on, but something done by restorers is dipping in Future floor polish. It is thin enough to fill the cracks and dries to a hard, shiny surface. It definitely does not harm (craze) the acrylic like CA glues can do.

That´s what I did, dipping in Future /Glänzer floor polish. But it don´t go into the cracks. Even in a vacuum chamber I couldn´t force the polish into the cracks. (like the car glass guys do with epoxy on the real car windshields do)

[Idris]

....between 75 and 90 degrees Celsius it just becomes soft and went banana. I think, when the softening point is reached, instead of filling the cracks inside, it just follows the internal tensions and shrink together.

TCorrect. It is because it softens before it melts.

[Idris]

I wish I had a Matchbox window to test it on, but something done by restorers is dipping in Future floor polish. It is thin enough to fill the cracks and dries to a hard, shiny surface. It definitely does not harm (craze) the acrylic like CA glues can do.

That´s what I did, dipping in Future /Glänzer floor polish. But it don´t go into the cracks. Even in a vacuum chamber I couldn´t force the polish into the cracks. (like the car glass guys do with epoxy on the real car windshields do)

A number of possibilities for the lack of success:
1) The vacuum wasn't deep enough. (I don't think this would be the problem though. They pull a vacuum on car windscreens because the crack doesn't go all the way through, meaning there's nowhere for the trapped air to go when they inject the liquid.)
2) The floor polish was too viscous to enter the crack. (The windscreen material is very mobile, and fills up the hairline cracks by capillary action.)
3) Floor polish did enter the crack but, because it does not have the same optical properties as the plastic, light continues to reflect from the broken surface, keeping the crack visible.

[GHOSTHUNTER]

Here is what Paul Carr says...

''Plastics used through the years varied, early days 1960's polystyrene was used which is brittle and snaps or cracks easily. In late years windows that were enclosed were moulded in polystyrene, windows that were exposed were moulded in flexible plastic like ABS and Nylon, windows that are cracked or damaged in any type of plastic I would say impossible to repair are. I am not sure what materials the reproduction / spares guys use as I have never handle one.''

So the one in question is going to be Styrene, ABS or a Nylon based plastic. Nothing morre specific I'm afraid.

Ghosthunter.

[Idris]

So the one in question is going to be Styrene, ABS or a Nylon based plastic. Nothing morre specific I'm afraid.

In this particular case, we actually have enough information to be able to identify the plastic concerned. The key to this is the glass transition temperature, which can be thought of as the softening temperature.
For polystyrene it is about 105 degC, for ABS about 100 degC, and for nylon 70 degC.
Based on the information given above, it therefore seems highly likely that the window insert is made of nylon.

[AJR]

Repair the crack with EMA solvent repair.
Use very sparingly just to seep into the crack.
It doesn't matter if some gets onto the surface but let it dry and don't try to wipe it off.
Let the plastic harden for a few hours then rough up the surface with fine emery board.
The plastic glass will now be scratched and opaque.
Next use a polishing board to polish out all the scratches and the crack.
Both the fine emery and polishing board can be found on opposite sides of the same emery board used by women to do their nails.

[GHOSTHUNTER]

''used by women to do their nails''

Some of us little men use them on our nails as well...

Ghosty.

[Idris]

''used by women to do their nails''

Some of us little men use them on our nails as well...

Do you file your nails?

No, I simply throw them away!

[Tinman]

I do my own nails too but I don't go as far as buffing them. I will admit to having a pedicure done about every three weeks. Since the lock-down, the wife has reluctantly had to take over that duty. However, while those files can be good some some things in modeling, I prefer to use wet sanding for plastic. Start with 600 grit and work up to 1000 followed by polishing compound (the stuff one uses to do headlight lenses is great) and a buffing wheel on the Dremel. Then a quick dip in my clear high gloss floor polish and I'm done.

When I polished out the headlamps lenses on my 2007 vehicle (in 2018), I tried one of those kits that comes with a buffing pad that goes on a cordless drill. The results were not as good as I expected. I started over, wet sanding by hand with 600, next 800 and lastly 1000 grit sand paper. I followed it up using the polishing compound from the kit and a small buffing wheel on the Dremel. They came out looking like new. That's the same process I now use on all plastic, large or small.

[DrJeep]

I saw a video on YouTube of someone making a replacement plastic canopy for a Ford pickup using a silicon mould and epoxy resin. Very effective, though time consuming and expensive in materials. Definitely easier to find another Ford Group 6 to dismantle!