No, he didn't. He said he sanded very lightly, as Marvin's instructions suggested, but we haven't used wood conditioner on any of the pine that we've stained. Thank you for the link! After reading it, I'm a little confused: does conditioner help softwoods absorb stain? The article seems to imply that it helped smooth the differences between earlywood and latewood?

I'm not a fan of the conditioners.

If there is glue or filler on the surface of the wood can make it difficult to stain.

What type of stain is it? How are you applying it?

If you could get a few sample piece's from Marvin to play with first would be idea.

The Marvin Line is wood and would accept stain easily but I believe the other lines Integrity/Infinity would require a gel stain?

It's the "regular" oil-based Minwax Wood Finish stain, a mix of two shades. He applied it a foam brush (which is the same method we've used on boards and trim). It's so odd that the one piece took it and the rest didn't!

Thanks for suggestion to ask Marvin for some sample pieces! That's a great idea.

Interesting about the difference between Marvin and Integrity; I was told (and my order form) says the interior is "bare pine" and the website says it's stainable; the instructions specify nothing about the stain except to follow the directions provided by the stain manufacturers (https://www.marvin.com/WebDoc/Paint%20and%20Stain.pdf).

I don't know much about stain; what would make a gel stain work when a regular one isn't?

This is from the owners manual found on Marvins website "Stainable, paintable products feature EverWood, an interior
engineered wood grain surface that requires a paint or gel stain
nish to be applied before or immediately after installation "

Edit..... that info was On the Infinity owners manual. Integrity doesn't mention Gel stain

I checked the Integrity by Marvin website again, and the only interior options are bare pine or primed wood; it's definitely not primed! I had folks from two different Marvin dealers come out separately and, given the goal of matching the other four sliding patio doors in the room (which are 40 year Marvin doors), both independently suggested the wood-Ultrex Integrity doors, assuring me that they could be stained - so these doors really ought to be stainable, I'd think! If only we could figure out how.

We stained ours without any problems. The painter did use some type of conditioner. The Integrity owners manual points out this may be desirable depending on the Stain's recommendation.

I called Marvin and they were puzzled too. The person in customer service "personally" recommended using a conditioner. She said if that didn't work, to call the dealer who sold the door to have them take pictures and information and send to Marvin, and eventually Marvin would replace the panels. That's not a desirable outcome, obviously (the installation cost and painting the exterior trim and all the work that went into getting them in place!), but I appreciate that they will stand by their product.

Don't see the conditioner helping.

I'd try sanding a little more or trying a wiping or gel stain. I just stained some pine and had no problem getting it as dark or light as I wanted. Not a fan of sponge brushes, maybe trying a chip brush and let stain sit.