If it is a dark dish towel that doesn't let light through. If the bulb sees enough light it will likely sprout a leaf and you are trying to get the bulblet as big as you can before using energy to sprout leaves. This year I had a bulblet start to put out a tiny leaf while the bulblet was small. I pinched off the leaf and I made sure it was in a dark place at which point the bulb started bulking up and using more of the scales reserves to build the new bulblet.
