Chrysotypes are prints made using gold to produce the image. When prints are made on photographic paper then the layer of ink sits on top of the paper and, over time, these can fade. Chrysotypes, as well as other alternative processes, work by coating cloth based papers with a sensitizer which is then absorbed into the substrate of the paper. In other words the print become part of the structure of the paper and it will last as long as the paper does.

As already described in the history section this is not a new process but has been refined, by Mike Ware, to make manageable prints mostly without the use of dangerous chemicals

Mike came up with four different versions of chrysotype:

Version 'S', where the 'S' stands for Sodium. This version produces prints which can contain split toning, giving reds in the shadows and blues in the highlights. It is also possible to produce prints which are entirely pink through to magenta or ones which are deep blue.
Version 'M', where the 'M' stands for Methyl. This version produces more monochromatic prints and uses a chemical which is highly hygroscopic. It is really aimed at drier environments and I can only produce Version 'M' prints in winter, when central heating reduces the humidity in my workroom.
Version 'P', where the 'P' stands for pH. This version uses the acidity of the solution to control the contrast and is a much more involved process than the preceding two.
Version 'A', where the 'A' stands for Ammonia. Adding gold compounds to ammonia can create fulminating gold. This is highly unstable and very explosive and because of this Version 'A' has not been published.