14/07/2014 at 20:27 #10226
I have been stripping off 50 years of varnish from A115 coach roof to reveal this solid and beautiful structure which I’m planning to epoxy and then high gloss varnish. The trouble is there are some black marks which wont sand out
Does anyone know any methods of removing them? please have a look at my pictures.
14/07/2014 at 21:19 #10227
Have you tried oxalic acid, it does a good job on stained wood. Some years ago I obtained some from a local chemist but a visit to the computer may give you more options.
15/07/2014 at 16:36 #10228
As Colin says oxalic acids the way to go not sure how easy it’s to get hold of as it’s classed as a poison, some years ago I got some from a furniture restorer. Even if you cannot get the stains out Id still go for the varnish option the staining adds character!
15/07/2014 at 17:44 #10229
there are plenty of Oxalic Acid suppliers on the internet, I checked after I sent a reply. You should not need too much as it is better to dilute and apply several times, you don’t want too much bleaching.
Good luck and I hope to see the before and after results on the website.
18/07/2014 at 19:05 #10230
The black stains are caused by mild steel staples which were used during manufacture to hold the second layer of veneer while the third layer was added. As a result these marks are usually near the centre line or at the joint between components. You will be able to partly remove the staining but it will always come back unless the staples are removed from the lower layer. However there may not be much of them left by now!
The oxalic acid is the correct way of minimising the staining. I have used bleach in the past. Either way it needs washing well and drying afterwards. Otherwise just live with the staining – it is part of the character of the boat!
As far as finishing afterwards. I would use a clear varnish. My coachroof is coated in traditional varnish. Six coats, and an extra coat every year. It is much easier to renew the surface yearly – to retain the UV resistance – than to let it deteriorate and have to strip it back again. Incidantally try not to sand too much off – or you will go through to the middle layer of veneer. You certainly dont want to have to strip it back too often.
I have used boiled liniseed oil as a primer coat in the past. Then overcoat after a few days with normal varnish.
If you want to use epoxy. You could roll on two or three layers of epoxy to soak into the wood before applying 2 component epoxy on top. You still need lots of coats (6?).
I have been reluctant to use a glass cloth with the epoxy because I have had trouble getting all of the air bubles out from under the glass cloth. Others have used it with varying amounts of sucess.
19/07/2014 at 12:22 #10231
Hi Trevor & Colin,
Thanks again for the expert advice. I will have a try with the acid and then see how we go.
01/08/2014 at 22:32 #10232
Lots of work! I’ve used bleach for changing the color of stains but it never seems to get back to the same grain appearance. If it’s still structurally ok I’d call them character marks and varnish over. Trevor’s suggestion to use boiled linseed as a primer is good advise. You might be pleased with the look of that.
I’ve had good luck painting over a few coats of UV protected epoxy too, but I’m not going to suggest you do it. It’s your call. It’s a lot more work to keep the epoxy coat smooth.
03/08/2014 at 14:03 #10233
I can add a bit more to this discussion. It is best to use a linear polyurethane (LP) coating over bare wood that has been encapsulated with epoxy resin. I have also used varnish (phenolic resin base mixed w/tung & linseed oil) to coat epoxy resin. It results in a slightly darker stain.
The oil based varnish stretches more than the wood, and the epoxy will stretch too.
In the future I’ll only use epoxy if I plan on sheathing or painting with LP, but I have not had a problem with either oil based enamel or clear varnish over wood that has been sealed with epoxy (kind of like using epoxy as the primer). I sand the epoxy with increasing grit sand paper, usually 80, then 100, 150, 220, & 330. I believe the advantage of LP over epoxy is because of a chemical bond but I can’t say for sure.
Some folks use the LP over the oil based varnish and claim it”s better UV protection and brighter. I can’t speak from experience on this approach.
It will be easier to strip it down again in the future with only oil based varnish. You’ll need a good respirator to avoid lung cancer and a lot of acetone and sand paper or a grinder to get the epoxy off if that is ever needed.
I have a solo12 dingy that shows the difference in varnish over bare wood vs. over epoxy, because I used epoxy as a sealing below the waterline. The difference is subtle. I’ll post a photo when I figure out where the wife hid the camera.
16/08/2014 at 10:05 #10234
Hi Robbie, Hi All,
Obviously very interested in how you go with your coach roof. I am about to do the same to Mary. The varnish (and I think it is oil based) looks like it is peeling from sunburn. After much deliberation I am going to go with an oil based varnish with lots of coats and a good few thinned ones to start with. I am stripping the old varnish with paint stripper as I fear my outer laminate is very thin in places.
I think I am going to use skipperpaints (Aemme) Starwind Tung oil varnish with extra UV protection. This brand is easier to find in Italy and it seems pretty good. I have booked time off at the end of September so any mistakes you can prevent me from making would be most welcome.
Keep us posted…
20/08/2017 at 18:59 #10235
In 1985 I sanded and repaired coachroof to wood, lightly stained it, gave it a coat of SP resin, then fibreglass scrim, 2 more coats of resin then 5 coats of 709 2K Polyurathane varnish, last two coats sanded before applying varnish with 320 paper in a DA sander.
Apart from considerably adding to it’s strength it has been maintenance free to present time. All coats were done within 24 hours of each other to ensure a chemical bond.
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