Are the corners of the boards square angles? If so, that may be where the splinters originate. First remedy would be to round over all those edges. The appropriate sized roundover bit in a router would be used. One that has a guide bearing and would cut a gentle round over edge on each board(probably both boards when the router is placed in the gap between the boards.

I know Ipe is sold as the best non splintering wood available, but wood is made of fibers, ipe has very small, strong fibers, and will splinter more as it ages.

Are you sure it's Ipe? We've been supplying Ipe for almost 30 years and have never heard of anything like this.

I have an ipe deck and handrail around a guard which had been down for over 10 years. I pressure wash it every couple of years as pollen and dust collect on it and being in the Pacific NW, the rain we get promotes a thin mossy growth which is slippery when wet. However the pressure washing does create a slightly rougher texture, different from when it was new and dry. And ipe being what it is, a tough as nails hardwood, the slivers created from pressure washing can be really sharp and painful. So yes, I am looking for an easy way to 'calm down' the surface of the ipe, but it sounds like it will be something that reoccurs when pressure washing. I too have heard of the orbital sander route as a cure and will give it shot soon.

Sold a lot of lumber back a few years ago and I have never heard of it "splintering" either. It does not have the type of grain that splinters. typically any wood that "splinters" from power washing means the pressure is turned up to high.

I just bought 2x4 ipe from Advantage Lumber. It is now instalked as handrails and it definitely splinters. I have two bandaids on my fingers from just running my hand lightly down the ipe railing cap. I'm hoping to find a solution.

I have a 10YO Ipe deck that probably was improperly power washed. It gives splinters like crazy. If you drop something on the deck, you will probably get a tiny splinter on your knuckel when you pick it up. A young kid ended up in the ER with dozens of tiny splinters in his feet. I've had multiple people in the deck business tell me they have never heard of this happening. And, yes, I'm sure it's ipe.

I have a Ipe deck with a Ipe 5/4 x 8” railing. I installed it myself in 2001. The railing cap has one board that is guaranteed to give you a splinter if you touch it. Compared to the rest of the boards it has an unusual swirling grain to it, which I’m sure is the reason it’s splinters. I’ve tried sanding oiling and now I am working on replacing it unfortunately, it’s the longest board on the railing 18‘2“ and the Ipe of 2001 is hard to duplicate because the dimensions are now different a 5/4 x 8“ piece that was 7 1/2 by 1 and 1/8 is now one by 7 1/8 by 1” so very hard to match it at the splice. I’m trying to find a custom piece and it’s getting very expensive at over $600 for one board.