HOW TO REPAIR GLAZING – OR MAKE YOUR OWN!
Model Rail’s expert modeller George Dent is often asked for tips on repairing damaged glazing. Here are a couple of techniques that can be translated to different scenarios.
I’m sure we’ve all done it at some point – smeared glue inadvertently onto a model via our fingertips. When the paintwork is affected, it creates a certain problem. A water-based glue like PVA, and some epoxies, can be washed away with soapy water before it dries. But most solvent-based glues will have to be tackled when fully dry.
Abrading and restoring the sheen with a clear varnish coat may be an option, or a little repainting may be necessary. However, that’s not our problem here, as this demonstration concentrates on what can be done if the glue has stained the glazing. There’s certainly no option of making a repair with a fresh coat of paint in this instance!
I’m often asked how glazing can be repaired, following scratch damage, clouding through over-exposure to UV light or solvent fumes, or the dreaded sticky fingerprint. In many cases, the damage can be reversed by careful abrading and polishing, as long as the damage isn’t too deep. A crack right through the glazing may be a step too far, but most scratches or glue damage – although it may look severe – is likely to be fairly superficial.
The Hornby Mk 1 coach featured here has been performing gauging trials on one of my new layout projects, so it has been exposed to rougher handling than would normally be the case. Accordingly, the glazing has become scratched in a few places but, worse than that, I also managed to smear contact adhesive onto a couple of windows.
After cursing mildly, there was nothing to do other than leave the model overnight to allow the unwanted glue to cure. There was certainly no point in trying to wipe it away – that would only make matters worse. I would have to remove the glazing and abrade the clear plastic until the glue and scratches were removed, before polishing the material to regain its transparency.
To do this, we need a full range of abrasives, ranging from coarse to super-fine grits in gradual increments. Padded sanding pads are ideal and they’re freely available from model and craft stores. However, I found a bumper pack on Amazon for a few pounds. These pads are often used by manicurists, so it’s worth shopping around to find value packs with as many grades as possible.
Indeed, working through copious different abrasive grades makes it easier to achieve a flawless finish. Sure, it takes time and effort, but the results are worth it. Moving through the grades, in 100 or 200 grit increments, allows the marks imparted by the previous grade to be removed. With soapy water as a lubricant, it’s amazing how smooth a surface we can create.
That said, even with hours of diligent abrading, the plastic glazing will still require some extra help to regain full transparency. That can be achieved by dipping or painting with a water-based clear finish, such as the famed Johnsons Klear floor polish or Deluxe Materials’ Looks like Glass. Once dry, these coatings also provide a protective barrier for
the glazing, but they do require a little skill to apply without creating streaks or brush strokes. Dust can be troublesome too if it gets into the wet coating before it dries.
Instead, polishing the clear plastic provides a simpler option, albeit a more labour-intensive one. Once I was sure that the abrasives had removed all the damage, and the successive grits had not left any marks behind, the glazing was treated with three grades of Tamiya’s polishing compound (Coarse, Fine and Finish). A matching pack of polishing cloths was used, which are colour-coded to match the packaging of each polishing compound.
The cloths aren’t essential – a clean cotton rag will suffice – but I do find them effective when working with the paste compounds, especially when buffing up the surface. The polishing compounds contain microscopic abrasive particles, which carry on where the abrasive pads left off. Once you get to the Finish compound, this imparts a lovely sheen to the surface.
Incidentally, the polishing compounds are also fantastic for finishing off paintwork, if you desire a showroom finish (they’re used extensively by automotive modellers). So, if you’ve had to abrade the carriage’s paintwork as well as the glazing, the finish can be restored with the polishing compounds.