A wood conditioner is a product that is used to prepare wooden surfaces for staining or painting. It helps to reduce blotchiness and uneven absorption of the stain or paint, making the finish smoother and more even. Full definition
We did not use wood conditioner and didn't have any trouble with the stain being blotchy. (lehmanlane.net)
I used another chip brush to apply a pre-stain wood conditioner as this agent promotes an even, uniform stain over the wood and helps to avoid streaks and blotches in the stain. (allthingsnewinteriors.com)
I applied one coat of Minwax pre-stain wood conditioner followed by 2 coats of Minwax dark walnut stain. (hersite.info)