Postby stuartp » Wed Feb 03, 2021 9:01 pm
1st idea (for a styrene wall) - cut the shape of the arch out of styrene sheet, cut the mortar courses between individual stones with either an Olfa cutter (or similar) or a triangular needle file, round off edges and distress stonework to taste. If you need a bit of relief on the faces of the stones either use a bit of filler or styrene shavings dissolved in liquid poly.
2nd idea, for any material - mask off around the shape of the arch, thickness of the tape used will be the depth if the finished arch so you may need more than one layer, or use insulating tape. Fill the bit inside the masking with filler, when the masking is removed the filler remains in relief. This works really well for concrete lintels on brick styrene sheet, not tried it for an arch yet. Cut mortar courses and carve/sand to taste.