One of the techniques that I am experimenting and playing around with in painting the Sector Mechanicus terrain is salting.
The technique and the idea behind it is simple enough. Essentially what I want to achieve is some kind of "masking" of random areas of the paintwork. I paint over them in a normal manner, but once done, remove the masking area to create a rough or chipped appearance.
With salting, this is achieved through application of salt. There are various types of salt available of course, ranging from regular granular table salt through to rock salt and various sized chunks in between and beyond.
The key thing with salting is that I want to achieve a random appearance. Hence it is necessary to think about the size of the salt grains to use. Here, I am using a blend of table salt and small rock salt that can be seen in the images below.
To attach the salt to the undercoat paintwork, I have simply used tap water. Dip a medium sized brush in to the water, then dab on some salt to the brush, and then apply to the paint work. I have deliberately experimented with very little water in some areas -- this leads to concentrations of salt that retains their original shape; and plentiful water -- this dissolves the salt in the main parts and makes it lie flatter on the paint surface. I anticipate that the latter (lots of water) will also be more regular shaped chips whereas less water will lead to more irregularly shaped chips.
Once the next layer is applied over the top of the undercoat and the salt, I will go back to the dried paint and use an old toothbrush to chip off the salt underneath to (hopefully) reveal parts of the undercoat.
Given the hot weather at the moment, I may wait a few days before doing these next few steps though.