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Is there a metod to fix the cracks on a windscreen insert, like this one from a Ford Group 6 ? The dipping in "Erdal Glänzer" (the name of Joes wonder stuff here in Germany) is OK for scratches outside, but didn´t go inside the cracks. I even tried the process in a vacuum chamber, but didn´t work either. (sounds like sophisticated high tec, but it involved a empty marmelade glass and a vacuum cleaner )
I tried very liquid super glue, but this was only a big mess.
Any ideas?

the problem is that, just like with car windscreens, for an invisible repair, you will need a material with exactly the same refractive index.
I wonder whether carefully applied heat, leading to local melting and sealing of the crack by capillary action might work. (Probably best to practice on a few beaters first! )

Depending on the size and angle it has: I have cut out the offending section and replaced it with some thinner clear plastic. Cuts needs to be exact and some windows are too curvy or don't allow enough room to hide the seams. That one would be difficult.

Heat sounds interesting. I think, acrylic shrinks before the melting point, but nevertheless i will give it a try.

paelzermaen wrote:Heat sounds interesting. I think, acrylic shrinks before the melting point, but nevertheless i will give it a try.

Yes, it will shrivel up and be totally ruined.

Tinman wrote:

paelzermaen wrote:Heat sounds interesting. I think, acrylic shrinks before the melting point, but nevertheless i will give it a try.

Yes, it will shrivel up and be totally ruined.

If that's the case, how was it moulded in the first place?

Idris wrote:

Tinman wrote:

paelzermaen wrote:Heat sounds interesting. I think, acrylic shrinks before the melting point, but nevertheless i will give it a try.

Yes, it will shrivel up and be totally ruined.

If that's the case, how was it moulded in the first place?

In a controlled environment, like a mold for example.

Let me try again.
If acrylic shrinks on heating, does that mean that it is moulded undersized, expanding when it cools, or does it only shrink when it's reheated having previously been moulded?

First level moulding it oversized or undersized in theory works, but is it then possible to control cooling for the shrinking/expanding to finish with the correct size for fitting into the model, interesting.

Ghosty.

This is so far from my expertise that I hesitate to comment... My very limited reading of some of the science is that melting the surface could in theory work, but that it would need to be extremely well controlled to a very precise temperature in a very localised area. That would need some specialised equipment and it would be easier just to buy another Ford Group 6 and salvage the glazing! We've all seen what a match or soldering iron does to plastic like this, and I think that's because the local temperature is too high and it melts and then burns. I'm not sure it's actually shrinking when it melts - I think acrylic or whatever plastic this is must be a normal material that expands with heat. I don't understand the moulding process at all! Now if only we knew a chemical engineer...