I've never heard of washing ipe with tsp before installing....

Hi Bill Vance,

When we sell Ipe, we don't recommend washing Ipe with any type of solution other than a specific cleaner and brightener for hardwoods. They are made to not react adversely with hardwoods like Ipe. Depending on how you received your Ipe, it should have just sufficed with a bit of soap and warm water.

We've found that a light prep sand with a medium grit sandpaper will clean up the bare timbers and also open up the grain to better absorb product. Very fine finish paper is not recommended and will actually polish the Ipe because the material is so hard and the grain is very tight. 100 grit is about perfect for prep. Some air dried Ipe has sticker marks and the prep sand will remove these and any water marks or imperfections as well. We have always been partial to single stage penetrating oils designed for hardwoods. In addition, staging the material for a few days in the shade if possible will allow the product more time to absorb. Fresh product in the hot sun is not a good recipe. We have not found the need for cleaners or chemicals and do not recommend anything not strictly designed for use with hardwoods.

Bill,
Also since you said you were washing the decking in your garage make sure you do not store the wood in your garage. The humidity and moisture levels are very different in your garage and will cause your Ipe to move undesirably if it is not acclimated outside where it will be installed prior to installing. If you need we have a helpful page with detailed instructions and videos that will help you:
http://www.advantagelumber.com/ipedeckinstall.htm