I am looking for a way to put down a strip of adhesive on the tab of handmade envelopes. I would like to have the adhesive remain dry on the envelope and only become tacky when it is licked/moistened-- just like on regular envelopes.
This has historically been done with gum arabic, but I can't find a "recipe" to properly mix the gum arabic for this application. Moreover, gum arabic seems to come in different forms (powder, grains, or liquid) so it's not obvious how to get started with using it as a lickable adhesive. It seems that gum arabic is mostly used as a paint additive these days.
Does anyone know how to make or buy this type of adhesive and have instructions for its proper application?
**** UPDATE ****
I (mostly) followed the instructions that were kindly provided by @Nothingismagick.
I followed the instructions in the answer. Everything went OK until I tried to dissolve the yellow dextrin. 25g of dextrin and 50ml of water produced a mixture that was hard to dissolve. I got impatient and added a LOT more water to the dextrin.
The end result was a solution that was too thin. It just soaked and stained the paper without producing a lickable layer. I put the jar on a radiator without the lid for a few days and this reduced the volume by half. The solution did get thicker-- like maple syrup. This works much better, but I think I should reduce it even more. Here's the final result.
I will try again and be more careful/patient when mixing in the yellow dextrin and the water!