Varnish Advice

[RickS]

My cratch board was installed Feb 22 and I was planning to give it another coat of varnish this year when the sunshine is a bit more consistent.

I noticed today that along the edge of the outside bottom beading there are a couple of small dark patches. Not too worried as I will let them dry out - if that is the cause - before varnishing.

The varnish used when the board was installed was Ronseal Exterior Varnish Satin Clear, which is water-based i believe.

My question is whether i should continue with this varnish or go for something possibly more durable, possibly not water-based. I'm not sure if I can put solvent-based varnish over the water-based stuff already on, or if I would want to, and would appreciate any advice

Cheers

[Sea Dog]

Oxalic acid is the stuff for removing the black staining on the wood. Comes in a white powder for mixing with water - you don't need much.  I got mine from eBay. You'll find videos on YouTube showing how to use it.

[Tracy D'arth]

Strip all that rubbish water based "varnish" and use a microporous finish like Sikkens.  Sealing wood outside in a nonpermeable finish causes rot.

Edited May 10, 2023 by Tracy D'arth

[blackrose]

What about yacht varnish? Is that permeable or not?

[Pie Eater]

I have always used Sikkens stain (as Tracy said)

[Tracy D'arth]

28 minutes ago, blackrose said:

What about yacht varnish? Is that permeable or not?

No, rubbish these days.

[blackrose]

1 hour ago, Tracy D'arth said:

Strip all that rubbish water based "varnish" and use a microporous finish like Sikkens.  Sealing wood outside in a nonpermeable finish causes rot.

 

Ok so this stuff isn't a varnish at all?

 

I varnished my interior window trims with a can of old yacht varnish so I think it was the proper stuff, but even with that eventually moisture creeps underneath. So perhaps a non-varnish finish is better. 

 

When I worked at a Thames boat yard we varnished the perimeter teak deck boards of a 120 year old steam passenger boat and just accepted that areas of varnish had to be repaired every year. The technique that I was taught was to gently scrape off damaged varnish with a hot air gun and a scraper and then sand a feathered edge and just patch varnish a few coats.. You had to look pretty closely to see the repair.

 

 

[BEngo]

Strip it, then apply Epifanes varnish ( the variety with UV filter) the way it says on the tin.  Or use Le Tonkinois as it says on the tin.  Either way you will apply a **lot** of coats🙂, but it will look superb,  last ages and be simply repaired.

 

N

 

[DandV]

I have,  and are continuing, to use a variety of varnishes for a variety of very high UV outside applications.

The most durable by far is a marine moisture curing polyurethane, and a huge advantage is that it is possible in the warm long daylight conditions to get 3 of the 8? required coats on in a day (.300 micron dry film thickness.)  And there is  no requirement to degloss previous coats if recoating within 30 hours.

Very very expensive, but in our harsh  very high UV marine environment here is achieving 6 to 8 years life until the top layer of the wood cells seem  to lose adhesion with the cells beneath leading blistering and sheet failure especially around any dings. 

Certainly it is the preferred varnish for most of our heritage boat fleet.

 

Currently I am  waiting for a fine break, tommorow? to put another two maintenance costs on the mahogany on the yacht on an area that had been revarnished about 2 years ago with 7 coats.

Removal however  is not easy because it is so tough rather then hard. 

 

Oil based one pot premium marine air curing polyurathane varnish in the same harsh conditions lasted only about 4 years.  And then it was also difficult to remove, especially in the areas not subjected to high UV induced degradation. The one coat per day and sanding between coats is a distinct disadvantage .

 

8 coats of the same varnish lasted about 4 years before total failure on a extremly exposed outside kwila/merbau balustrade.

 

Here I next used Rustins teak oil here but even with maintenance recoats every year it had failed after 4 years, but on garden furniture in a sheltered location it has been satisfactory for eight years with maintenance coats every two years. Easy to apply and once weathered it becomes brittle so easy to remove.

 

5 years ago the same balustrade was recoated with 6 coats of Sikkens Cetol Marine and with 2 maintenance costs per yeari it is showing no signs of failure.

Easy to apply but a day between coats is an inconvenience.

Are now using Sikkens Cetol HL for the annual maintenance coats as here it is about half the price of the Marine grade.

 

The vertical surfaces of a cratchboard are not subjected to the same extreme exposure as  horizontal surfaces, and here the standard cetol range is far cheaper then anything proclaiming marine on the tin.  

 

 

 

 

 

[MtB]

6 hours ago, RickS said:

My cratch board was installed Feb 22 and I was planning to give it another coat of varnish this year when the sunshine is a bit more consistent.

I noticed today that along the edge of the outside bottom beading there are a couple of small dark patches. Not too worried as I will let them dry out - if that is the cause - before varnishing.

The varnish used when the board was installed was Ronseal Exterior Varnish Satin Clear, which is water-based i believe.

My question is whether i should continue with this varnish or go for something possibly more durable, possibly not water-based. I'm not sure if I can put solvent-based varnish over the water-based stuff already on, or if I would want to, and would appreciate any advice

Cheers

 

Paint it the same colour as your cabin for an easy life. 

 

You know it makes sense

 

 

Edited May 10, 2023 by MtB
Fiddle with it...

[LadyG]

Depends on the finish you want, Sadolin , the premium stuff is pretty good as a preservative, and stains which might cover the black. You need to remove the water based stuff by sanding

[Tony Brooks]

6 hours ago, LadyG said:

Depends on the finish you want, Sadolin , the premium stuff is pretty good as a preservative, and stains which might cover the black. You need to remove the water based stuff by sanding

 

I am not convinced that sanding is the best way, especially as others have suggested scraping.

 

The painters at the hire fleet, where we had some varnished wooden boats, the painters would collect our worn out all hard hacksaw blades and break them into small lengths. They took a short length of wooden batten, cut a slot across it at one end, and the hammered the teeth side of a piece of blade into the slot. they then ground the free side of the blade to a sharp right-angled face.  two could strip one side of a 30 footer in a day, resharpening as needed.

[Tigerr]

I would scrape off the cheap water varnish, and then either oil or varnish with top end like epiphanies. Lots of coats. I use a sharpened triangular paint scraper, re sharpening as I go. Much much faster than sandpaper, easy on the hands, and better surface prep. 

[cuthound]

In the 9 years I have had my boat I have tried Yacht varnish (lasted 2 years), Le Tonkinous twice (lasted 3 years each time) on the cratch board and this year will use Sikkens as it has so far lasted 3 years on my iroko garden gates without cracking or peeling.

[Peanut]

11 hours ago, MtB said:

 

Paint it the same colour as your cabin for an easy life. 

 

You know it makes sense

 

 

The most sensible answer, Katy Louise has acres of varnished teak. Nothing lasts, and it is an ongoing job, just like the Forth bridge.  A cratch board looks really good when painted in traditional colours and patterns. It will be much easier to maintain.  Unfortunately, Katy Louise would look c**p if I painted over It all.

 

[Hudds Lad]

27 minutes ago, cuthound said:

In the 9 years I have had my boat I have tried Yacht varnish (lasted 2 years), Le Tonkinous twice (lasted 3 years each time) on the cratch board and this year will use Sikkens as it has so far lasted 3 years on my iroko garden gates without cracking or peeling.

Which variation? Will need to do our cratch board soon so interested in what you'll use  

[cuthound]

Cetol HLS Plus followed by Cetol Filter 7 Plus.

[Pie Eater]

17 minutes ago, cuthound said:

Cetol HLS Plus followed by Cetol Filter 7 Plus.

These are the ones that I used annually.

 

 

[DandV]

Awlwood moisture curing polyurathane.

2 coats applied today 3hrs apart on a 14deg C day on the skylight after degloss sand and masking.

On the gunwale the toe rail varnished 5 years ago with the same stuff has faded and gone slightly milky. Big job with tungsten carbide scrapers coming up.

In the background a new female intake on the youth sailing vessel Spirit of NZ are taken aloft.

[RickS]

Thank you everyone who posted advice - very useful.

To be honest, I wasn't expecting the fairly universal advice of 'scrape it off and start again' (I paraphrase). This is a much larger job than I expected after only a year.

Thanks again

[MtB]

2 hours ago, RickS said:

To be honest, I wasn't expecting the fairly universal advice of 'scrape it off and start again' (I paraphrase). This is a much larger job than I expected after only a year.

 

 

This is why (as I mentioned before), paint is such a Good Idea. 

 

We all learn this lesson eventually  

 

 

 

 

[BEngo]

Modern paint is little or no better than most modern varnish  when it comes to staying stuck to things.  Oh for the days of white lead primer!  The disadvantages of paint are that you can't varnish over it and that you need three different tins to put it on.

 

N

[MtB]

2 minutes ago, BEngo said:

Modern paint is little or no better than most modern varnish  when it comes to staying stuck to things. 

 

You're doing it wrong!