Loco cab glazing ? - Kristal Klear, Glue 'n' Glaze etc.

[Atlantic 3279]

Has anybody used these successfully? - It is supposed to be possible to glaze cab spectacles and other small windows by simply wiping one of these "polymer film forming" liquids (PVA solution by repute) across the hole and allowing the liquid film to dry to the clear state.

Never having tried the method, and unable to but either product locally, I decided to try out the method on some scrap pieces using a slightly diluted sample of the white woodworking glue that I already had, in this case "Evostick weatherproof wood adhesive". The "windows" I've produced, none more than a few mm across, have dried to a sufficiently transparent state but there is a very definite concave lens effect because surplus solution not forming the thin film across the middle of the opening "pooled" against the frame around the egdes of the window. Do the pukka proprietary glazing solutions also produce this concave lens effect, or is the "trick" perhaps to try to remove the surplus liquid whilst it is wet so that only the amount essential to maintain the thin film remains? I've also wondered whether a spot of detergent in the slightly diluted PVA would do anything to encourage a more even film to form across the full width of the window aperture, without the pooling at the edges.

Any advice gratefully received.

[richard]

I've used the Testors version successfully in holes as big as the spectacle glasses on the Y7 in 7mm scale (about 1cm across). Yes I think the trick is probably the proportions of things like PVA, water, and detergent.

There's always a bit of a miniscus even with the commercial formulations. Drying position also helps.


Richard

[Atlantic 3279]

Thanks Richard - Meniscus is exactly the term I should have used, but it never entered my mind, perhaps because it is now 29 years since my last physics lesson......

As an experiment last night I put a second coat of my white glue over the dry clear film that had formed in a couple of the window apertures, whilst these were lying flat. As I hoped, free from the effect of the forces that get the original liquid film to span the empty gap, this second application pooled nicely in the depression in the middle of the original meniscus. I hoped that this would solve or greatly reduce the concave-lens appearance once it had dried. Unfortunately, it hasn't been successful for two reasons. Firstly, despite 24 hours drying time for the first film of "weatherproof" glue, that original film softened, expanded, and therefore sagged and wrinkled in the presence of the additional wet glue, and it has not shrunk back to a tight, flat layer as it has dried. Secondly, the increased thickness of the combined films now betrays the fact that the glue dries slightly "milky" rather than absolutely transparent.
However, I'm now inclined to try pooling gloss varnish on a couple of my other original single concave films. I hope this won't soften the glue and it should dry clear and shiny.
Even if I do finish up having to use a two-applications process in order to produce convincingly flat clear windows, that is in my mind easier than messing around trying to cut clear glazing sheet to exact-size irregular shapes and then trying to glue that glazing in place without spoiling it. After all, it isn't always possible to get rear access in order to hide an oversize piece of glazing at the back of the window aperture, and even if it is this sometimes makes the glazing appear too deeply recesssed, because of course it is!

[jwealleans]

I've used the Humbrol product and the MicroScale and found the latter to do a better job. As you're finding out, it does pool and distort. I use it on round spectacle windows but, for example, on the Adams Radial on my WB I shaped pieces of cobex as the liquid glazing - if it had held over such a large area - would have looked odd. This was done with it and I think you can see that it's not transparent enough to be really convincing.

IIRC I cut out pieces of glazing material for the side windows once I'd seen these. Fine for smaller windows but not anything over a few mm square would be my verdict. Make sure it's thoroughly dry before you weather it as well.

[davidwest]

I used Kristal ceer on the front spectacle plate of a DJH A2.

[Atlantic 3279]

I suspect cab spectacles are the limit by the liquid glazing method, and even they will be imperfect to intense scrutiny. My attempts to pool gloss varnish to "flatten out" and "shine up" some dummy A4 cab side windows weren't satisfactory. Even when laid flat, an application of enough varnish to actully fill the hollow in the meniscus simply showed how strongly the varnish then tries to creep up the edges of the window frame, forming its own annoying concave meniscus. With the shrinkage that occurs as the varnish dries, the dip in the middle looks as bad as ever .

Typical really, nothing easy ever seems to give good results .