Hello there again!, Rafael here. In this short article I will describe how to weather sandbags with acrylics, Indian ink(optional) and small amount of dark brown pigments.
step 1: make sure you have primed, painted the sandbags with your desired colour (in my cased I used dark yellow) and varnished it to protect the paint and remove any mistakes if need be.
(Primed, painted and gloss varnished)
step 2: apply a dark brown wash all over the object; be generous as washes tend to loose colour once they are dry plus you can always remove the excess with a wet cotton bud.
step 3: in this step I did used Indian ink to gain even more depth through the bumps and cracks. Although not need it I like to use this product because the pigments are much smaller than normal wash giving just that little extra details.
step 4: after everything has dry properly it might look a bit too dark depending on your personal preference so in my case I applied some Tamiya “buff” and brush dried in the areas I wanted to bring back some colour. I kept gently blending away until I was happy with it.
In many cases this should be enough for a pretty good results but if you feel that it is still too dark you can always apply a lighter wash as I explain in the next steps.
step 5: apply a diluted dark yellow or desert yellow colour. For the purpose of illustration I decided to apply this extra wash because I wanted a brighter colour and tones.
As I said, if you are already happy with the results on step 4 you can just skip this one and jump to step 6
step 6: here is where we use the brown pigments to give that realistic look to it. You can find a huge variety and you can even create your own ones (will show how on another article!). Apply it as needed and wanted.
step 7: final matt varnish coat to seal it all off and that’s it!
PS: in this hobby there are many different techniques in which one can achieve the same results, this is just one of them. Take what you need and experiment until you find the way works best for you!