Wednesday, 8 May 2013

1/72 Unimodel BA-10 Armoured Car Pt. 5 - Vinyl rot prevention

As a newcomer to modelling and it's dark arts I happen across brief mentions in modeling forums of things I do not understand but worry me a lot. 'Track rot' sounds very nasty indeed but I really don't have a clear understanding of what it exactly was/is, but the various reports of vinyl tracks disintegrating and rotting plastic parts they adjoin were a concern.

So imagine my shock when - while posting up the progress of my UM BA-10 armoured car on the Society of Gentleman Gamers forum - I discovered that the vinyl tyres of my model were exactly the type material that causes this sort of disintegration. Chris Steadman (of SoGG) commented on my project...
"On the UM kit, did you use a barrier between the vinyl wheels and the plastic? Are you aware that they are known to interact and that the plastic dissolves with time? PVA apparently acts as a good barrier. There are also reports that washing the vinyl parts well, helps to reduce the effect. Also, when you paint the model, any paint with a solvent base will attack the vinyl parts."
Eeeek! This was enough to send any kitnoob like myself into a mild panic...But I calmed down!

And so, my solution was a bit belt and braces but I hope this works; I detached the tyres from the plastic wheels and coated the wheels with a gloss varnish to act as one barrier between the materials, then I sprayed the wheels their base colour (Humbrol acrylic Light Olive) to act as a second barrier. I also sprayed a light coat of varnish over any other area - notably the front fenders - where the tyres would come into contact with the main model.

Having done that I next turned my attention to the tyres themselves. As recommended I washed the tyres in soapy water and then, once dry, I painted on a thin solution of PVA just on the inside of the tyres where they would come into contact with the plastic wheels.

Coating the vinyl tyres with a thin layer of PVA glue to act as a barrier.
I was going to weather the tyres using a AK Interactive enamel based weathering wash - for dust effects - but I will avoid anything like this now. Instead I will use chalk and conte crayon dust brushed on over a very thin coat of PVA to hold the dust in place. Bit of an experiment there but let's see how that turns out.

So, little hic-up. To be honest I was skeptical about the merit of the vinyl tyres right from the start, tyres are just as easily modeled using hard plastic and paint effects. In any case they are a pig to fit and deform - I will probably try to avoid them in the future (though I can't really avoid vinyl tracks unfortunately).


  1. Good work Stephen, and what a effort!

    Track rot was a real issue back in the day, but you do not hear too much about it nowadays.

  2. I was told that this wasa problem with the first run of rubber tyres by this manufacturer, and that later runs are meant to be OK.