How to clean unpainted wooden stairs?

Damp-mop with water, using a flat-head mop and microfiber pad or a microfiber string mop that has been thoroughly wrung out. Move with the grain, and control the amount of cleaning solution by using a spray bottle, aiming for a heavy mist or gentle squirt of about a half teaspoon per 2 square feet. No need to rinse. No need to buff either, but cloth diapers and soft socks do work well here.

Here you go! Good luck to you.

https://www.wikihow.com/Clean-Unfinished-Wood

http://www.homefloorexperts.com/clean-untreated-wooden-floorboards/

https://www.hunker.com/13419895/how-to-clean-unfinished-wood

I use Bona for hardwood floors since stairs are wood anyway. So simple.

Hello S, here's a recipe for cleaning unpainted wood

https://www.youtube.com/watch?v=QKyV9jzh0LM