I just got alcohol inks for the first time and I am overwhelmed on how to use them on postcards!
Has anyone used alcohol inks on the back of postcards or even on the front of handmade cards? Do you use card-stock with gesso or something like yupo paper?
Please share your creations if you’d like 
I have not but I’m very curious. I discovered them recently on an art journal video. They were sprayed on, with some paper to cover an area that they wanted to keep clean. Hopefully this bump will encourage someone to answer!
A question…. does anyone experience ‘bleed-through’ to the picture on the front? Especially from alcohol ink pens?
I suspect that watercolours, pencils and felt-tips (water-based pens) will be fine?
I am interested in how well your chosen art medium behaves?
Thank you in advance for any responses. 
I think alcohol ink pens are q risky, especially when the postcard materials are thin kind of paper. but cardboard material are fine for the alcohol ink I think
I use alcohol ink markers on most of my store-bought postcards and have never experienced bleed-through. However they do bleed through my cardstock (220 GSM), so for handmade cards you would probably need thicker paper or something to cover the back. 
I’ve received a store-bought (glossy) card with bleed through to the picture side from alcohol ink on the back, so I do think this is a concern. I’ve never seen it with water colour (but I have made postcards buckle from too much water), or felt-tips.