Does Xtracolor enamel go off in the tin?

[ckw]

A couple of months ago I airbrushed a Do 17 using Xtracolor RLM 70 and 71. When compared to other models, the colours looked a little 'faded' and the contrast between the two was less than expected. I put it down to something I did, and anyway, real paint fades in the field anyway.

 

Move on to last night and I started to paint an He 115 using unopened tins of RLM 72 and 73. These tins had been purchased in an earlier modelling life (25 - 30 years ago) but I'd never got round to using them. The paint had no colour at all and came out as shades of grey ... and not even greenish grey! 

 

So my question is, can colour fade from enamel paint in a sealed tin? (Note that the paint was perfect in every other way apart from colour). If so what is the shelf life for a tin of enamel paint? 

 

Of course it is also possible I bought tins which had been wrongly labelled by Hannants, though I'd never had that before.

 

I'm not bothered by the loss of these two tins - I've ordered replacements - but recently I have started buying multiple tins of the same colour (due to suppliers running out of stock and reduce postage costs), and some of these tins may remain unopened for some time.

 

Cheers

 

Colin

[Graham T]

I use a lot of Xtracolour & never encountered this but tbh I don't think I've ever used a tin that was that old!

[Casey]

The only explanation that comes to my mind is that they used Ultramarine Blue in the mixes which can desaturate in presence of acidic environment over time which may be possible in that old paint.

 

Some pigments are lightfast, but are not chemically stable - Ultramarine is a prime example here. I hope @Jamie @ Sovereign Hobbies could chime in there, considering his woes with PB10

 

Interestingly, Ultramarine Blue is quite stable in acrylics due to themselves being alkaline enviornment, but the same reason removes real Prussian Blue pigment from acrylic range.

 

Edited November 30, 2022 by Casey

[Jamie @ Sovereign Hobbies]

On 11/30/2022 at 4:59 PM, Casey said:

I hope @Jamie @ Sovereign Hobbies could chime in there, considering his woes with PB10

 

Hi Casey,

 

I have to admit the reported issue here of the colour desaturating to grey inside a sealed model paint tin is a new one on me, and I'd venture that mis-labelling is probably the culprit.

 

It's quite true about ultramarine though - it definitely tended to wash-out to grey on RN warships at sea, early on at least, but the paint composition was described in Admiralty documentation as "oil bound water paints", a sort of early emulsion. The degree however I think is debatable as the evidence is mostly in the form of colour film which isn't very reliable a source anyway. I'm sure you're aware also that some chrome greens are known for shifting too as they're made by precipitating chrome yellow on to prussian blue to make green, only the yellow can attack the blue shifting the colour from green to yellow.

 

[ckw]

Well I've received a fresh tin of RLM 72, and it is certainly green compared with the old tin of grey paint. Tempting to put a sealed tin aside to see what happens in 30 years, but I doubt I'll still be around to complete the test.

 

Cheers

 

Colin

[ColonelKrypton]

This has been an interesting discussion.

 

I have never experienced this phenomenon with any paint and my use of Xtracolor was long ago and I no longer have any left. 

 

Perhaps there might be some value in contacting Hannants / Xtracolor and pass along your observations. There maybe someone there who deals with their paints and pigments that may find this interesting.

 

cheers, Graham