I keep reading about sanding wood before staining. If I'd like to stain brand new wood molding is it still necessary to sand first? The wood molding is already very smooth

 

The average person would "think" it is smooth and ready to stain. However all trim has come through a shaper or router of some type that puts chatter marks on the trim to some extent. These marks may be hard to see when looking at the raw wood (because novices dont know what to look for) but become more obvious when it is stained. This is because the blades that shaped the wood create a pattern where the wood is compressed or burnished. Sanding removes this and creates a more consistent surface that will accept the stain better, more uniform.

Some people accept those marks as normal and unavoidable, but most any finish carpenter or self respecting painter would never skip sanding stain grade trim.

There really aren't many products that are ready to stain. Anytime I have ever thought I could skip sanding, I have always regretted it halfway through staining when some hard to see blemish suddenly stands out like a sore thumb once stained.

 

I would add that while you should sand first, you don't want to sand it too fine as that can cause the grain to close up making it harder for the wood to accept stain. 120 or 150 grit is fine enough, always sand with the direction of the grain!

 

Thanks for the feedback. SO you would only use a 120-150 grit or you would first use 120-150 then follow it with a 220 grit?

 

Depends on the product and type of wood but generally I only sand trim ONCE, with 120 grit. (With the grain only, as marksr mentioned) I find this is sufficient for most trim, and since time is money, I'm not going to spend time sanding again and again unecessarily. On veneer doors, which are generally pretty smooth I only sand once with 150 grit. The only thing I EVER sand with 220 grit is the end grain of a board. 220 closes the pores and causes the wood to be lighter / absorb less stain. End grain will more closely resemble the face grain this way.

Since finer grits cause the wood to absorb stain at different rates, uneven sanding can sometimes show up once you stain. Another reason I generally just give everything a once over with just one grit.