Acid free may be a problem as most are buffered and I am led to believe the Calcium Carbonate buffering is an issue with fading. There are very pricey non buffered acid free mats. As well, the vast majority of historical daguerreotypes are kept in leather and wood cases which would be quiet acidic. I would wonder about your cardboard mat; most historical mats were metal, often brass or high rag paper. I suspect the key is the sealing off of atmosphere.
As regards the colour wheel, I meant achromatic, not Ortho. Presently I am trying to assess a daguerreotype of, I think, a Calvary Lancer of Second Empire France. The various units had tunic fronts of pink, yellow, red, blue etc.
It would be very helpful, in this type of situation, to have a comparison wheel of colours to determine the shades of grey in an achromatic rendition to expect for say a pink or baby blue of the same luminance. I would expect pink to come up as dark grey and blue to come up as white, but I have not really found a good comparison tool. Of course I am assuming that your emulsion is actually achromatic and not orthochromatic.
It occurred to me that a portraitist using achromatic materials might want to know how various shades of colour are going to come out. Although I suspect lipstick was not used much by your subjects, the oriental dress might well be a mid red or green . A achromatically lighter (blue) dress might have allowed for less exposure and a more contoured face on the lady. if desired, of course.
Kindest Regards
