Stain under varnish
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- Posts: 5
- Joined: Mon Mar 23, 2009 4:33 pm
- Location: Berkshire
Stain under varnish
On a recently bought boat I have dark stains under the varnish that I would like to get rid of before varnishing ( one or two pot I have not decided yet). The wood is sound and it is not the white "bloom" you get when damp has been drawn up to the varnish surface usually by the warmth of the sun. Almost certain it will have to be taken back to bare wood to do this although the varnish itself is not bad and would prime a coat of varnish if I ignored the dark stains.
Re: Stain under varnish
It's almost certainly damp.
Scrape the vanish back and leave the wood to air for a bit and it will clear up.
The more difficult problem is "where did it come from?" It may be either that the old varnish has cracked and become slightly porous, or it may be that the damp is coming through from the other side.
See the starboard bouyancy tank, the slightly darker patch, here (this prompted a rebuild...) :
That tank was no longer watertight and water had got into it after a capsize or three...
Scrape the vanish back and leave the wood to air for a bit and it will clear up.
The more difficult problem is "where did it come from?" It may be either that the old varnish has cracked and become slightly porous, or it may be that the damp is coming through from the other side.
See the starboard bouyancy tank, the slightly darker patch, here (this prompted a rebuild...) :
That tank was no longer watertight and water had got into it after a capsize or three...
Last edited by ACB on Mon Mar 23, 2009 6:50 pm, edited 1 time in total.
F 3163 "Aquarius",
IC K229 nameless for the time being
I14 K377 "Mercury" - long term rebuild project
Re: Stain under varnish
On the MOGO there were black marks under the paint. I sanded these over lightly and the warm weather has done the rest. I think they just needed to 'breathe' to dry out. I'm fairly confident they came from whjere the hull had simply been lying on the grass. The paint over them just fell away.
The Peril
Agamemnon
Lovely little Cadet
OK 1954
Xena Warrior Princess
Finn 469
Laser 2
Wayfarer World
Agamemnon
Lovely little Cadet
OK 1954
Xena Warrior Princess
Finn 469
Laser 2
Wayfarer World
Re: Stain under varnish
On my old 12 I found that stripping the varnish with a hot air gun did both jobs at once. When I had to leave it for a year due to a back injury, the black stains were harder to get rid of, but careful applications of diluted Domestos (other brands of bleach based cleaner are available) did the trick.
John Kn
John Kn
Re: Stain under varnish
It could well be stain. When I obtained Merlin 908 (1958) the decks had been stained and varnished, badly!! But what was worse it looked more like boot polish! I stripped back to bare wood and then used P40-60 oxide paper and a shed load of elbow grease to rub back to original wood colour. (Tip: gently brush off the sanding dust as it make ideal filleting power when mixed with epoxy) then apply single or two pack varnish. The big plus to using 2 pack on older boats, according to Mervyn Allen (big on vintage merlin restoration), is the resins absorb into any minor abnormalaties that come with older boats providing additional strength.
Good luck
Good luck
Re: Stain under varnish
Oxalic acid can be used to lighten wood that is stained. Search for Oxalic acid on this site and you will find loads of info.
Roger
Roger
Hornet 191 Shoestring,
Hornet 595 Demon awaiting restoration
Hornet 610 Final Fling
Hornet 353
Hornet 595 Demon awaiting restoration
Hornet 610 Final Fling
Hornet 353
Re: Stain under varnish
I keep trying Oxalic as I hear from many places that it is the stuff to use but have never had much in the way of results with it. However if you need some there was a chap on e-bay that was selling it for a very good price - I was amazed to have it delivered the next morning when I had only ordered it at 4.30 the night before.
Graham T
Osprey 1340, Osprey 1245, Osprey 55, Miracle 1358, Laser heap, ancient Mirror kit half assembled, Project Miracle in need of decks........
Kielder Water Sailing Club
Osprey 1340, Osprey 1245, Osprey 55, Miracle 1358, Laser heap, ancient Mirror kit half assembled, Project Miracle in need of decks........
Kielder Water Sailing Club
Re: Stain under varnish
Amazing that you can get it on ebay when it is a pretty potent poison and you can't get it from a chemist!!!
- Ancient Geek
- Posts: 1133
- Joined: Wed Sep 10, 2008 9:50 am
- Location: Sletten,3250, Denmark and Hampshire GU33 7LR UK
Re: Stain under varnish
This will be brief (Blackberry!) The answer is a lemon! Cut a lemon in half and rub one half on the stain cut the remaining half into quarters put one quarter into a large glass add ice Tanquerays gin about 1/3 of the way up fill up with Fever Tree Tonic sit back and enjoy when you have finished the drink the stain will have gone wipe down with thinners turps or whatever you use finish in the usual way, may as well use the other quarter of lemon too.
Simples.
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- Posts: 5
- Joined: Mon Mar 23, 2009 4:33 pm
- Location: Berkshire
Re: Stain under varnish
Oxalic acid is good for rust too. But because of its on the poisons register I have used lemon juice including Jif and white vinegar. So it depends if you prefer pancakes to chips. But thanks for your help.