Tutorial: making realistic natural stone walls in scale

I can spare you trying out the various methods you can find on the internet because I found a great way of doing walls!

I wanted mine in a limestone look like you find them in Southern Europe.

First I ordered a stencil from Bromley Craft Products together with a bag of Sandstone Brick Compound. Mind you, it is not quite as yellow as on their picture - but is slightly pinkish. I added some yellow acrylic paint to the mixture before spreading it on the foam board. I used a spatula and did not even out  - just rough and as it comes. Like this I do not have an even stone surface.. some are a little thicker, others have 'creases', etc.

Once dry, I colored it with greyish water color and dry brushed with raw umber (or Vandyck) and yellow acrylic paint.

Next step is to spray it with a matt acrylic varnish. That has to be done twice - leaving it to dry completely between the applications. It is important that you actually see the varnish forming a film! The stones need to be absolutely water tight.

If the rocks are not totally waterproof this is what will happen...

For grouting I used normal tile white grouting from the hardware shop, adding a bit of grey powder so that the contrast is not too stark.
Cover liberally (haha, as if there was a choice...) but scrape off excess.

Once the grouting is REALLY dry, use a sponge or micro fibre cloth to uncover the stones!

Voilà!