Teak prep before Cetol?

[Tessellate]

Anyone have recommendations about how to clean up weathered teak prior to applying Cetol? I already stripped the old, peeling varnish using a heat gun (12+ hours of work!).

See pictures attached. The parts of the teak toerail that were exposed have weathered to gray (and slightly black in some places, where rain water tended to sit). It sounds like I could try teak cleaner products but those may be kind of harsh to the wood, and pricey. The other option is a bleach + laundry detergent solution (mentioned in the Don Casey book I have).

If I try bleach + soap, how does application of that work? Just brush it on and let it sit for a few minutes and then wipe off? I'm kind of skeptical it will do anything but I can give it a try.

I emailed Sikkens (Cetol manufacturer) about this but they didn't respond. But I'm set on Cetol because we've been happy with it on our hand rails. I'm not obsessed with getting this perfect (to me cosmetics are second in priority to everything else) - but would like to at least do it halfway right given all the varnish stripping work I already invested.

Also, it'll be 1-2 months before I can apply the Cetol, because we're in rainy season now (rains about 5 out of every 7 days). Would you apply teak oil (after cleaning) to protect the teak until the Cetol can go on, or would that just interfere with Cetol adherence?

[Tessellate]

Hmm, no replies? I guess I should've posted this in Construction, Maintenance & Refit rather than Product or Service Reviews & Evaluations. I know there are tons of people who know about teak prep.

[bletso]

I had the same thing on Vigah after leaving it too long. Sanded the old Cetol and wood bare and applied 4 coats Cetol. Best to do the annual maintenance coats.

[Copacabana]

I wouldn't oil it if you plan on using Cetol later. I would try an oxalic acid solution to bleach all the wood to a uniform colour and then a general sanding of all of it before applying the Cetol. This, of course, after a soap and bleach cleaning and thorough drying.

[Dymaxion]

Lots of sanding with sheets folded up as needed got it down to a mottled but varnish free surface. Then a 3M "scotch brite" pad which gets into the dimples and pits better than sandpaper can. Get them at an autobody supplier since there are several grades of coarseness they will stock, unlike hardware stores. When worn down a ways save them for flatting in between coats. Four coats Cetol. Done 2 years back on east coast, boat under cover every winter, so not a tough test. Have fun, looks great once done.

[Lake-Effect]

When we got our boat, the teak trim was in rough shape. i replaced some of the worst bits, sanded everything smooth, but didn't worry too much about any greying or uneven tone. Number one thing was to have it dry and smooth.

I used (and am still using) Cetol DEK satin finish - their "natural" shade - which I have left over from a deck and porch renovation. The teak ends up a warm brown/honey tone and any teak discolouration seems to be minimized. The finish isn't super-glossy but water beads on it. We're quite happy with it.

The initial application was maybe 3 coats, then I've been doing recoats or touch-up every 2 years or so. If I was a better human being, or was on southern salt-water, I would apply a coat every year.

[LakeSuperior]

Originally Posted by Copacabana

I wouldn't oil it if you plan on using Cetol later. I would try an oxalic acid solution to bleach all the wood to a uniform colour and then a general sanding of all of it before applying the Cetol. This, of course, after a soap and bleach cleaning and thorough drying.

I think I agree...if I understand

1. bleach stripped wood to uniform color with oxalic acid solution
2. wash with soap and water and let dry
3. light sanding overall with 120 grit
4. wash with soap and water and let dry
5. apply 3 to 4 coats of Cetol

[Cavalier]

Originally Posted by Copacabana

I wouldn't oil it if you plan on using Cetol later. I would try an oxalic acid solution to bleach all the wood to a uniform colour and then a general sanding of all of it before applying the Cetol. This, of course, after a soap and bleach cleaning and thorough drying.

^^this. "Zud" works well for this application (oxalic acid), and is cheap! Once you've pre-wet the teak, you can apply it with a sponge-scrub, and then agitate thr surface after a couple of minutes and then wash off again. Don't let it dry on there. When it washes off, all of the black and grey will go with it without removing any of the pulp from in between the grain.

[lancelot9898]

Here is how I prep the surface.

First I use a heavy duty scrapper and most all prior coats can be removed without the aid of a heat gun, but it is available if needed.

Next I've used 80 grit sandpaper in an electric palm sander followed by a 150 grit sander( some hand sanding depending on geometry)

I follow up with a bucket of water only using a 3M scuff pad, then a wet rag soaked in that water and then a dry rag

Let completely dry with aid of sun....then apply 3 coats of natural and finally 2 coats of gloss (the gloss is important to help protect the finish from UV) maintenance coat twice a year of just one coat gloss ( prep is just using the scuff pad, wet rag and dry rag) maybe some sanding if warranted

[atmartin]

I prefer to wash with TSP (Trisodium Phosphate) after the Oxalic Acid bleaching.

No sense sanding with 120 or finer grit before your final water wash, the water will raise the grain equivalent to 80 grit or less.

[SVTatia]

Originally Posted by lancelot9898

Here is how I prep the surface.

First I use a heavy duty scrapper and most all prior coats can be removed without the aid of a heat gun, but it is available if needed.

Next I've used 80 grit sandpaper in an electric palm sander followed by a 150 grit sander( some hand sanding depending on geometry)

I follow up with a bucket of water only using a 3M scuff pad, then a wet rag soaked in that water and then a dry rag

Let completely dry with aid of sun....then apply 3 coats of natural and finally 2 coats of gloss (the gloss is important to help protect the finish from UV) maintenance coat twice a year of just one coat gloss ( prep is just using the scuff pad, wet rag and dry rag) maybe some sanding if warranted

++!

This is exactly what I did and this is what I recommend as well.
If you use any kind of acid you may remove some of the soft wood and you get an uneven surface. The sanding mentioned above is not hard to do.
I would apply 4 coats of natural and 3 coats of gloss to give you several more months before the maintenance coats are needed.

[Tessellate]

Thanks.

I hadn't heard of Zud (oxalic acid cleaner). It's nice and cheap ($3-4 for 16-oz).

Sounds like some people do bleach + soap, some do oxalic acid, and some do both. I guess I'll give bleach+soap a try and if that doesn't work try the Zud. I don't think I need to do very much sanding, as the toerails are already pretty smooth after peeling the varnish.

When we did Cetol on our handrails we didn't do any cleaning to remove the black spots (there weren't too many) but after 2 years or so there are some small spots that show under the Cetol. So I think that's either due to poor prep, or perhaps we need the maintenance gloss coat more often than the 1x/year I've done.