The floor test I did in a previous post had interesting results.
Because the tile sheet was dried unattached to anything, it bent slightly, but held together. The gaps between the tiles widened as it dried - hopefully this would eliminate any cracking. You can now see a little daylight through some of the gaps, and the whole thing is slightly flexible and forgiving.
The problem is that the underside is not flat, as you can see in the second photo, with ridges where the gaps are - difficult to glue down :(
The extra separated tiles, however, each warped as they dried - again, difficult to glue down! :( My advice is, don't go there!!
So I did another test, using Jovi (as in the first test) and Paperclay. This time I glued them onto a board while wet, and tried three methods of marking the lines.
The top third is marked with a piece of veneer (less than 1mm thick).
The centre third is marked with veneer, but with a (loose but flat) layer of cling film on top of the clay. This smooths and rounds off the edges of the clay, and gives a type of bevelled effect. This also enlarges the gap a little more.
The lower third is marked with a piece of extremely fine brass sheet. I was hoping to give the effect of flagstones, where no mortar is needed (oh please, yes!!). The gaps still widened a bit, but are very crisp.
I have also tried painting the Jovi - it has a smooth surface, more like polymer clay, and shows every brush mark, and would not take a wash very well at all. If anyone can tell me what DAS is like, I'd be grateful :)
For painting I prefer Paperclay because of its absorbency - takes a light wash beautifully :)
For this technique I'd advise that you tidy all the intersections with a pin or fine toothpick at the leather-hard stage of drying. The more careful you are in the marking process, the less you'll have to tidy later. And make very sure that the marker is exactly the right length between the pinholes.
I'd also advise placing a flat layer of clingfilm between the wet clay and the paper pattern, and pricking the holes through both. The paper pattern buckles on the damp clay.
The gaps made with the veneer would need to be grouted - not my favourite activity!!
The gaps made with the brass sheet could pass for flagstones, not needing grout. I say this hopefully! :)
The Paperclay shrank more than the Jovi - the gaps were wider after drying.
So there it is so far. I hope it may help - sorry I get too pedantic in my explanations, it's a bad habit that I can't throw off . . .