Being a dye, SL will not harden. In fact, if it is applied with as
little solvent as possible, it will leave a powdery residue before
finishing. You can get it to the point where it doesn't penetrate at
all, but will leave a fine dust of its particulates.

I have had a different experience than those here with SL. I have
used it extensively on exterior entry doors for new homes, replacement
doors and for restoration work. So far, no problems at all.

But SL is only as good as its topcoat. I have never used it but once
when I had anything but a UV resistant topcoat. I have used it under
exterior poly, and extensively under a post catalyzed exterior grade
conversion lacquer. Never a problem, knock on wood!

The point is that the dye is not a stand alone product. It MUST be
top coated, period. While I have found the SL brand to be very UV
resistant, it is essential that it be additionally protected with
another UV resistant finish as well.

I tested SL for my own use (before being sued for lousy workmanship by
irate clients!) by using the old tried and true "roof test" from the
old days. I took a piece of dried poplar and dyed it (I spray it) and
then finished it as I would a door with 4 coats of finish. I loosely
covered half of it with a piece of old tarp and left the other half
exposed.

On the roof it went, later to be moved to a shadeless, full sun and
exposure spot in the yard. It got full, S. Texas sun, downpours, more
sun, and then really hight temps as well. I tossed it back on the
roof when it was in the way and forgot about it.

About 14 months or so later, I pulled it off and looked at it. I was
surprised; the stain side showed little evidence of fading. Strangely
(maybe finish discoloration or wood reaction to UV) it was a little
darker in a couple of spots.

I have not changed my spray formula, method or topcoat since.

I have to agree with all of Leon's remarks. I think they are spot on,
and the most I ever see anyone finish ipe with around here is a thin,
oil based product from Cabot's.

Most of the other deck seals and colored "stains" are no more than
overthinned varnishes with colorant. Multiple coats simply peel off
around here.

Don't confuse SL with Transtint or other products that
specifically warn against using them where UV exposure can be a
detriment to the coloration. There are many documented stories on the
refinishing/finishing groups of guys that ferreted out Transtint (or
its non-UV resistant top coat) as the culprit when there was an
outline of an object left on a table by a sunny window.

Remember too, that when you use that type if dye, it is only good for
inside use, and that you will probably be using an interior rated top
coat. These will be harder than the ones you will use outside since
elasticity isn't required, but with NO UV resistance from a top coat,
the color of your piece will have no protection at all.

As always, just my 0.02.

Robert