Originally Posted by Irie
That is the question of the day !
Well...the whitish water streaks can show up in varnish and polyurethane finishes. The oil finish...dunno, suppose so, but much less likely.
Veneer over plywood...is it thick veneer like say 3/8"? Or super thin veneer (1/16" or even less). This makes a difference in how you treat it. There are some lovely teak plywoods out there--they're actually teak plys all the way through. They were more common 30 years ago than now, so it depends on when/where your boat was built if it has that. Much more likely to be a regular marine grade plywood with a teak or mahogany veneer front/back for the bulkheads. For the stairs...much more likely to be at least 3/8" thick. I digress....
We have terribly, terribly (did I mention TERRIBLY!) worn 3/8" teak sole over plywood sole panels. We're not bothering to refinish the panels until sometime next year--so our floor just looks yucky and old--but we've got so much else to do...I digress again...
The link I made to the Le Tonkinois product is a good one for your application. We have made new (solid wood) sapele companionway steps from the charthouse down to the main saloon and they were finished with this product. It is shiny (you can dull it to satin just by buffing with bronze wool or a high grit sand paper) but yet isn't slippery. It looks very good and seems to be wearing well. Our other companionway ladder from the deck down to the charthouse has a traditional varnish on it and IT IS SLICK!
so I will be putting Le Tonkinois over it shortly. Besides the place I linked to in the previous post, you can also find it here at this store
I've personally found scrapers (razer sharp ones) to work much better than sanding for varnish removal of any kind. Sanding is the last part done after the scraping does most the work.
If your boat's previous owner used polyurethane, Lord help you in getting the whitish finish off of it. Sometimes folks use various 2 part epoxy finishes that look great for a while and then end up with quite a whitish haze that necessitates removal.
Got some pics of your project? What kind of boat is it? How old?