Surf - when we buy an old boat, we have zero clue as to what was
done to it by previous owners or how long ago. The photos that I posted
of the ducer corrosion is just what I found - we can only draw our own conclusion as to how it happened.
I was not there, so I have no idea as to the mounting process that was done probably 5-20 years earlier.
I do know the difference in the popular caulks, so I can visually identify certain products. (most of the time).
and yes, you are so very correct in the daunting task of decyphering the instructions for the products we use.
due to the EPA and other government regulators, manufacturers must scramble to adjust their product
formulas to meet those specifications and still be as adequate to meet the consumers needs.
I have been a sign painter/fabricator and installer for well over 50 years and often
times we are challanged heavily to mount different sign materials to different surfaces with different methods.
this is how we (myself and colleauges) find out what works and what does NOT work for many products.......
Also, preserving and painting wood signs have their own inherent characteristics.
redwood and cedar will be preserved differently than plywood signs.
I have made some plywood signs 20 years ago and they are still standing today.
of course they need to be touched up periodocally, but the wood itself is still sound
after being in the harsh elements 24/7/365 for many years.
So, over the years, I have been exposed to several products that only work in the way
they were intended - anything else will be opening Pandora's Box of possible misfortune.
This why I advocate the saying: Read, Understand and FOLLOW the directions on the label
of any and all products you may use. They are there for a reason.
I have been an active member in the Sign Industry, Fine Woodworking and Wooden Boat arena since around 1980.
These are very fine places to learn just about anything wood related as well as preservation and painting techniques.
I also have been an instructor in wood carving, wood processing, preservation and painting since around 1990.
Spar Varnish is for exterior wood products
Urethane and Spar Urethane is for interior projects such as floors and furniture.
also I found out that some objects applied to a red brick building with 100% pure silicone will last forever.
the same objects applied a concrete block surface with 100% silicone will fall off in two weeks due to accelerated corrosion.
I guess the bottom line will be to read, understand and follow the instructions on the products you use.
If it says it may affect "some metals" I would only be guessing that they mean aluminum or copper.
jus my Dos Centavos on that there.
Edit:
a new product on the market is a lightweight product with thin aluminum
skins on each side and a foam composite core. Very weather resistant and strong.
we have a joke that goes like this . . . .
quick - go stick this new aluminum sign on the building using only 100% pure silicone. It should last 20 years.
- and then -
quick - go fix that new aluminum sign that just fell off the building !!!!! with bolts this time.
.
