Yellow Vacuforms

[OttovonLindberg]

On 3/17/2019 at 11:32 AM, Jonny said:

Hhhhmmm -

I have a 1/48 Czech Model Me. 309 kit that I bought cheaply a year or so ago off a stall at an airshow.  When I came to try to build it I found the vacform canopy to be yellowed. I left it on a windowsill for some weeks and it cleared a little.  Unfortunately I decided to do something else and now I find the canopy is back to yellow.

 

HOWEVER, sun /natural light *did* seem to improve the situation.  Whether it would if a built model is left in such a position I don’t know.  In my case such things are discouraged by SWMBO.

 

Does Czech Model still exist, does anyone know?  I suspect it’s now known under another name.

 

Jonny

Sorry for necroing, but I just got this kit too, and I have the same problem. The top panes are perfectly clear, but the further down you go, the yellower the canopy gets 

Edited February 5, 2021 by OttovonLindberg

[TheRealMrEd]

A thread which some may find useful:  HERE

 

Ed

[T-21]

I taped two well yellowed vac form canopies to an upstairs bedroom window. After a month exposed to sun and daylight all the yellowing has gone so it does work.

Edited February 7, 2021 by T-21

[dragonlanceHR]

13 hours ago, T-21 said:

I taped  two yellowed  vac form canopies to an upstairs bedroom window. After a month exposed to sun and daylight all the yellowing has gone so it does work.

Is this permanent or are they yellowing again?

[Graham Boak]

That's the first posting I've seen where it worked.  I can only presume it was a different material from the usual, which doesn't.  Where is the industrial chemist when you need one?

[Ed Russell]

I taped half a dozen different yellow canopies to a window starting about 6 years ago and none have improved. A friend in Cairns (where it is a bit more sunny) did the same thing and has same results so far after about 3 years.

[busnproplinerfan]

I think I saw s thread about this on here before. I have an H-13 Chech kit which comes with the optional yellow bubble. I’ll have to do the new one. Can the Durham be glued on?

[Graham Boak]

It keeps reappearing.  LIke all topics really, there is always someone to whom  it is new.  

 

What's a Durham, other than my home county?

[T-21]

Mine are clear at the moment ,too early to see if they will remain so, but i will dip them in  Future and hope that protects them.  One is an Aeroclub  1/72 Gloster Javelin  the other a Skybirds ? Percival  Prentice 1/72  so quite aged.

Edited February 7, 2021 by T-21

[Graham Boak]

The villains of the piece will have gone yellow by now, so you are possibly more in danger of varnish yellowing.  I think Future is OK...

[Work In Progress]

I've never owned any actual Future but I have many models using vac-form canopies and original Johnson's Klear with between a 20 year and 25 year track record of not yellowing.

 

I've never seen a Skybirds, Aeroclub or Falcon / Squadron canopy go yellow in all that time, only ones from Czech manufacturers, in my case Special Hobby. If it's a couple of decades old and still OK, it's not going to go yellow in any relevant timescale.

Edited February 7, 2021 by Work In Progress

[Luka]

I had a severely yellowed CMR Supermarine Attacker canopy taped to my window last summer, and nothing happened. It seems likely that the type of plastic used in Czech vac canopies in those days is the culprit of yellowing transparencies just as W.I.P. stated. 
Luckily I was able to find new replacement canopies, 
Another method would be to vacform new canopies using the old ones as a master, but by using thinner material for the new ones. PET bottle plastic can be used. The resulting canopy would be paper thin though, and much more fiddly to attach onto the model.

[robc]

48 minutes ago, Graham Boak said:

 

What's a Durham, other than my home county?

See the link in TheRealMrEd's post above.

 

Regards

[Ed Russell]

If you had visited the CMK premises in Prague a few years ago you would have seen a large roll of clear material for making vacform canopies. Looking at one thickness it was quite a pale yellow but the whole roll viewed as one was somewhere between buttercup and marigold.

There are umpteen threads on Britmodeller and elsewhere detailing the halogen chemistry of yellowing and why the yellowing is irreversible except by the use of some sophisticated and potentially dangerous chemical engineering.

[Graham Boak]

Let's not just blame the Czechs.  When i was at school in the 60s, one teacher brought in a box of old (pre-plastic) aero-modelling bits, including pre-formed balsa parts, metal engines/undercarriages (fairly generic) and a selection of vac-formed canopies.  They were yellowed then.

[Pin]

On 2/6/2021 at 7:38 AM, T-21 said:

I taped two well yellowed vac form canopies to an upstairs bedroom window. After a month exposed to sun and daylight all the yellowing has gone so it does work.

 

PET canopies are not decals, to the best of my knowledge UV exposure does not take the yellowing away. 

 

[Paul Thompson]

Never heard of one successfully sun bleached either. Must have got chemically lucky.  WIP, sad to say I do have some yellowed Aeroclub canopies. Not from any of their kits, but in a set of Spitfire variants, and one or two others. About half of my (far too many, much as I love them) Rareplane kits have a spectrum of yellowing, from just beginning to cloud through to a fully nicotine cloudy haze. Yet the others, some much older, are crystal clear, because they're not the same material, as referenced in this and countless other threads. The same applies to the Rareplane Dragon Rapide, where the fuselage halves were moulded clear. I have 4 kits, two are still fine, 2 are bad enough I'll have to replace the windows and canopy sections.

 

The one currently really bothering me is my Echelon Lightning canopy, to the extent that I've used it as an endless excuse for parking the build until I can fix my Mattel Vacuform, which I hope will be big enough that I can use it to pull a new one from a mould made by filling the yellowed canopy with Milliput.

 

Paul.