[Tony Wheeler]

At the risk of disagreeing I suspect we greatly overstate batch variation during WWII, as a convenient excuse for our own inability to achieve batch consistency, and our failure to even attempt standardization across the MV community. This is not intended as criticism - a host of factors conspire against us here, which did not apply in WWII.

One of these factors is our miniscule batch size, which multiplies the required accuracy of tinter measurement by many orders of magnitude. For example, one pint of yellow tinter in a 10,000 gallon production batch would probably equate to a fraction of a droplet in a 4 gallon batch. No paint shop machine can measure tinter that accurately, which is why house paint varies from batch to batch, despite being mixed to the factory formula. Another factor is continuous production, which enables continuous matching, and even mixing with the previous batch to achieve consistency. These techniques are simply not available in small batch production. Another factor of course is expertise and equipment - there's no comparison between the local paint shop proprietor and a team of scientists at the factory lab.

On the question of wartime conditions compromising batch consistency, this runs counter to our general expectation of milspec production, ie. more stringent than civilian production. Unless there's some particular "wartime" reason for long established companies to suddenly experience quality control problems not faced in peacetime, there's no reason to assume they did. The reality in wartime is technological improvement, not the opposite.

Rather than assume wartime inconsistency I think we need to recognize the enormous hurdles we face as restorers - miniscule batch size, complete absence of colour standards, reliance on 70 year old paintwork, etc. etc. We simply can't hope to approach the batch consistency achieved in large scale commercial production, any more than a homebrewer can approach the batch consistency achieved by large commercial brewers. Nor does it really matter, as Ron says - the only imperative is that you're happy with the colour yourself. Likewise your homebrew!