We had a brazilian walnut floor installed and finished with Bona Traffic Water-Based finish. 9 months later, we noticed riges popping up in between each board. I'm guessing that the ridges are finish. Overall, it gives the floor the appearance of being cupped. Has anyone heard of this happening or does anyone know what might cause this?

What may have happened is that when the finish was being applied 9 months ago, there may have been some very slight gaps between some of the floor boards. As the finish was applied, it seaped into these gaps. Now months later, the floor has expanded a little and forced that finsh that was between the boards up above the surface. This does happen. What is needed is to control the relative humidity to around 50%. After the humidity has been maintained at a constant for a few months and the flooring has equalized, the ridges could be screened down along with the rest of the floor and another coat of finish applied.

I should defer to Gary,but I am a bit intrigued by the fact that the ridges are said to be between each board. That would imply that there were gaps between each board;ie,all. Just a nit to pick.

This actually happened to me on a job the builder REFUSED to keep temperature controlled. Since the weather was mild, I proceded to install and sand the 3/4" by 2&1/4" select white oak floor. The day before I was to start applying the finish, it got real hot and the humidity dropped to 20%. Needless to say, gap city between the boards. As I was getting pressure from the builder and the homeowner, I went ahead and applied the finish. A few days later, the weather returned to normal and the gaps closed up, creating little beads and "ridges" of finish. So now I'm to blame and they want to know what I'm gonna do about it. Screen, pad, and recoat; what else can I do? Now, if someone refuses to keep the evironment climate controlled, I either get a waiver or tell 'em to get someone else who doesn't care.

The interesting thing about this situation is that the ridges did not show up for 9 months. 6 months after the floor was finished and climate controlled it was screened and refinished, yet the ridges have still appeared. They only appear at the edges of floorboards.

Nothing interesting about it.

The flooring has gained moisture, from a humidity gain and swelled.

The nature of the beast. It bit you this time.

The humidity may be the case. The humidity has been controlled at 50%. Is this too high for Brazilian Walnut?

Have you checked for moisture in the subfloor? Under the house? Your flooring is picking up moisture from somewhere, me thinks! What reading does your humidistat say? You'll need to investigate! Good luck!

Eperrel, You say you are guessing that the ridges are finish. "Overall, it gives the appearance of being cupped."
It the ridges are finish I think you would know. If it is finish coming up from the seams after 9 months, the finish must have not cured properly and now the floor is expanding and has forced the finish in the seams up.
What sealer was used with the Traffic? Bona DriFast Sealer(oil-based)is often used with Traffic and other waterbased finishes for a rich color and normally works great.
I tested DriFast Sealer and some other oil-based sealers on Brizilian Walnut and they would dry but remained very soft. I put Traffic on the sealers and it dried but stayed much softer than usual. I do not think Traffic that is cured properly would pop up between the boards.
We used waterbased sealer(Glitsa Snap Dry Sealer) and waterbased finish(Glitsa Infinity II) and it looks great and cured properly.
This job was a glue down to an aluminum deck on a large yacht(interior), 1500 s.f. of Brizilian Walnut 3/8"x2" solid,square edge,site finished. 700 s.f. was glued to two exterior decks. This wood is very stable outside at 98 degrees and 95% humidity and rain so it should not move much in your house. You may need to check for moisture intrusion and/or soft finish down in the seams.
Buddy

maybe somebody is damp moping the floor?
maybe this is expansion due to change of weather pushing finish up similar to that of raised checks?
maybe the floor is cupping slightly giving a reflection?