Useful tips for making scratches
Using apropriate material as hologram substrate and learning to use it correctly, may help to achieve the best results by means of increasing hologram dimensions and quality.
I found the plastic overhead transparencies to be apparently the best substrate for drawing holograms. There are several reasons, that involve the same process of making the scratches, and the viewing itself. In addition, surface of the overhead transparency is not as hard as the acrylic one, then the quality of scratches tends to be better (you should review the Beaty’s article and learn about “good” and “bad” scratches).
Protecting working media from damage
You should use a piece of thick transparent plastic to apply the compass tip, thus avoiding damage the transparence sheet. Dragging the piece over the transparency you can reach all centre points for drawing scratches, taking advantage of the whole sheet.