diy – How can I make my own coatings for handmade paper for inkjet printing?

No direct experience but I can give you a starting point. Inkjet paper has a few special properties and your paper will need to be a layered construction to be able to support a print.

Obviously you’ll have the paper base.

But if you just print onto this you’ll get ‘wicking’ or spreading of the ink so you also need a impermeable layer on top of the base. If memory serves me right, this is either Kaolin or Baryta.

This impermeable layer will need to be waterproof so you will then need something on top of that to hold the ink (and prevent it from spreading.) Gelatine is commonly used.

Then you may require some kind of upper coating depending on what finish you want on your paper (matt, gloss etc.) US Patent 5858514 may offer a good starting point.