Lickable glue for handmade envelopes (gum arabic)
tldr; Classical envelope glue is made with gum arabic and yellow dextrin. Both gum arabic and yellow dextrin are dissolved in hot water. To prevent rot, refine with copper ions and a drop of clove oil. Apply to paper.

100 ml distilled water
10 g gum arabic (powdered)
25 g yellow dextrin (or 20 g tapioca starch + 10 g sugar)
1 drop clove oil


You can purchase gum arabic online or at better art supply stores - take whatever form you can get. If it is in crystal form (semi-irregular rock-salt size) crush it with a mortar and pestle.) Use only distilled water. A copper pot is not absolutely necessary, but copper ions are antimicrobial and antibiotic. Clove oil can be replaced with peppermint oil or left out if you do not plan to store it.

Crush the gum arabic with a mortar and pestle and then soak overnight in a copper pot with 50 ml of the water. In a glass bowl, sift the dextrin (or starch and sugar) into the remaining 50ml of water and mix until the water is cloudy and no clumps remain. Heat the water and gum arabic mixture, but do not bring to a boil! Add the drop of oil and gently whisk in the dextrin with a stainless steel hand whisk. Continue whisking until the solution gels. Remove from heat and pour into a clean and dry mason jar.

When cooled, brush thinly onto your paper envelope and let dry (or use a blow drier to speed the drying). If it gets too thick, thin with distilled water. Keep cool and in a dark place. Do not freeze, use within 6 months.

Bonus: To make yellow dextrin, spread 500g of tapioca starch out on a dry and ungreased cookie sheet and put in an oven at 200 °C. Stir it with a metal spatula every 10 minutes until it has all turned a golden yellow colour. Remove from oven and let it cool down, then put in an airtight container.