Thread: Penetrol on wooden boats......

Penetrol is a oil based paint flow additive. It has no UV inhibitors if used alone. Penetrol is almost always used in concert with something else. You can oil things up if you like, but more often then not, these treatments don't last very long and can complicate coatings later in the project.

In spite of your friends recommended use of Penetrol, the best thing you can do is get the boat under cover, preferably a roof, not a tarp. A tarp is better then nothing, but most still let sunlight through them, which is what kills wood finishes.

With it under cover you can then access the separate elements of the boat and start scrapping and stripping the worn out finishes off the boat.

Penetrol and other straight oil finishes tend to pick up dirt if used by themselves.

They are really easy to add extra layers to, but you have to be careful to avoid runs onto painted areas as it makes a gummy sticky surface that is hard to clean up if left for a while. Easy enough to clean immediately, but neglected can be a pain.

It can prevent repairs that require the use of glue later as any glue will find it difficult to adhere to the oily surface.

Your friend is right about being able to coat it over with conventional paints and varnishes. I have used it a lot for a first coat under the normal quantity of varnish, but I don't think it is particularly good by itself.

The lack of UV filters is a serious deficit as this is what defines a good marine paint or varnish

Many of the similar products such as Deks Olje have a two part system where you start with the oil and then use a separate varnish like product to resolve the tendency of the oil picking up dirt.

Best wishes
Michael.

Deks Olje is marginally better then straight Penetrol. It's one of the best of the manufactured traditional oil finishes, but it's still what it is, some tung oils, Japan drier and a few other modifiers.

Brisbane seems to have a more moderate climate then I do, but not by much, so you'll be using these oil finishes at least twice a year, probably more if you want them to work the best at UV protection.

The best UV protection is a roof and walls.


You might have gathered I don't think much of these finishes and you're right. On strictly traditional craft, it's pretty much all you got, but given a choice, it's not much better then bare wood.

A real high solids content oil finish (which Deks Olje is not) will offer maybe a third of the protection that a varnish will. Secondly, certain types of bugs love to live in these types of oil finishes. They usually don't damage anything, but the wood does get covered with little spots (their bodies) which is a pisser if you're interested in a pretty finish.

I have an oil mixture that I use on traditional boats, that includes a pesticide, drier and more UV inhibitors then typical oil finishes, but of course it's also darker too. You can paint alkyds over it, though you'll want to prime well if using some types of polyurethanes and don't even think about acrylics without a barrier coat.

Thanks for your replies. It is a very confusing subject with so many options. I found Cetol made by Sikkens and wonder how good it is.
Sikkens has been around a long time and they make real good stuff. I used Sikkens paints in Germany and it always worked.
Has anybody here used Cetol?

Cheers
Reiner

Cetol is translucent paint. It protects better then varnish, but not as good as paint. Some folks use it over raw wood as a semi clear type finish, but many find the colors objectionable. They've noted this and backed off the color in one of their offerings, but it has even less protection. It's not their fault, because it's a functional difficulty of clear coating wood.

Yep, it's confusing. Simply put, paint is the best protection on wood. It blocks the UV rays from literally burning up the cellular structure of the wood (which is why it turns gray or black).

Prep under the paint has a huge impact, such as epoxy encapsulation, oil treatments, preservatives, etc. Epoxy encapsulation is the best protection under paint.

Of course the best paints are also the most expensive and difficult to apply well.

After these choices is a descending list of options. As far as just straight coating protection goes (paint): two part polyurethane, single part polyurethane, modified acrylic enamel, alkyd enamel and then acrylic (latex) are the best to the worst paint is terms of protection.

High gloss offers much better protection then semi gloss or especially flat paints.

As far as clear coatings go: two part polyurethane, single part polyurethane, shellac, alkyd varnish, acrylic varnish then the traditional oils is the descending order for these.

Cetol is in between paint and clear coats. It acts like a single part polyurethane, though I'm fairly sure it's actually a modified alkyd. I've used it once and can't stand the color and the way it washes out the grain. If I want to cover the grain, I'll use paint instead.