Brown wood stain on gelcoat.

graham

graham

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Anyone know how to get brown wood stain splashes off white gelcoat?
It's been there for several years where someone stained a wooden belting not using tape.
 
Poignard said:
Have you tried oxalic acid? That's pretty good at lifting out stains .
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Oxalic acid is good for "bleaching" iron based stains by changing the colour and making the product soluble, I doubt that the wood stain will succumb but maybe wrong. I suspect that it has permeated the gelcoat to some extent and short of an organic solvent removing what is left on the surface abrasion and polishing is the only way.
 
Fr J Hackett said:
Oxalic acid is good for "bleaching" iron based stains by changing the colour and making the product soluble, I doubt that the wood stain will succumb but maybe wrong. I suspect that it has permeated the gelcoat to some extent and short of an organic solvent removing what is left on the surface abrasion and polishing is the only way.
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"A colorless, crystalline powder that is a strong organic acid. Oxalic acid was first discovered in the extract from the wood sorrel plant. It also occurs naturally in rhubarb, spinach, beet leaves, Swiss chard, chocolate, cabbage, sweet potatoes, peanuts, cranberries, strawberries, and bell peppers. Additionally, several species of aerobic bacteria (Penicillium and Aspergillus), molds, and lichen excrete oxalic acid as a metabolic product. It is also a component in air pollution and acid rain. Oxalic acid is synthetically made from sawdust or by treating carbon monoxide with sodium hydroxide. Oxalic acid has many roles as a bleach, metal polish, stain remover, and mordant. It is used as a bleaching agent for straw hats, leather, and wood. Oxalic acid acts as a reducing agent for metal oxides to remove tarnish as well as rust or ink stains. It is used commercially as a laundry rinse, wood-bleaching agent, and calcium remover. Oxalic acid can remove some paints and varnishes. It is also used as a mordant in dyeing textiles and in the manufacture of ink. Oxalic acid was used in the toning solution for black and white photography. Since at least the mid-19th century, oxalic acid has been used on works of art: to remove rust and ink stains as well as to bleach leather, wood, papers, stone, and textiles; and to clean encrustations from wall paintings, ceramics, and sculptures. However, these treatments can leave oxalate residues that are difficult to distinguish from naturally occurring residues due to microbiological growth or air pollution. More recently, oxalic acid has been used as a mild hydrolysis agent in the preparation of natural dyes for HPLC analysis. "

http://cameo.mfa.org/wiki/Oxalic_acid


Certainly worth a try, I think.
 
Poignard said:
"A colorless, crystalline powder that is a strong organic acid. Oxalic acid was first discovered in the extract from the wood sorrel plant. It also occurs naturally in rhubarb, spinach, beet leaves, Swiss chard, chocolate, cabbage, sweet potatoes, peanuts, cranberries, strawberries, and bell peppers. Additionally, several species of aerobic bacteria (Penicillium and Aspergillus), molds, and lichen excrete oxalic acid as a metabolic product. It is also a component in air pollution and acid rain. Oxalic acid is synthetically made from sawdust or by treating carbon monoxide with sodium hydroxide. Oxalic acid has many roles as a bleach, metal polish, stain remover, and mordant. It is used as a bleaching agent for straw hats, leather, and wood. Oxalic acid acts as a reducing agent for metal oxides to remove tarnish as well as rust or ink stains. It is used commercially as a laundry rinse, wood-bleaching agent, and calcium remover. Oxalic acid can remove some paints and varnishes. It is also used as a mordant in dyeing textiles and in the manufacture of ink. Oxalic acid was used in the toning solution for black and white photography. Since at least the mid-19th century, oxalic acid has been used on works of art: to remove rust and ink stains as well as to bleach leather, wood, papers, stone, and textiles; and to clean encrustations from wall paintings, ceramics, and sculptures. However, these treatments can leave oxalate residues that are difficult to distinguish from naturally occurring residues due to microbiological growth or air pollution. More recently, oxalic acid has been used as a mild hydrolysis agent in the preparation of natural dyes for HPLC analysis. "

http://cameo.mfa.org/wiki/Oxalic_acid


Certainly worth a try, I think.
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Seems not surprisingly to confirm what I said, glad to know my education and the tax payers money was not totally wasted and that my memory is still functioning to a degree.;)
 
Fr J Hackett said:
Seems not surprisingly to confirm what I said, glad to know my education and the tax payers money was not totally wasted and that my memory is still functioning to a degree.;)
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I was not for one moment suggesting that what you said was wrong (I wouldn't dare!) only that oxalic acid has additional uses.
 
Fr J Hackett said:
Indeed it does, be careful not to eat to much rhubarb especially the leaves:D
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I am very fond of rhubarb but it is difficult to find a supplier. I once tried to grow some but the foxes ate it; apparently with no ill-effect.

Have you tried the Bon Maman rhubarb jam that is widely available in French supermarkets? It's very good.
 
Poignard said:
I am very fond of rhubarb but it is difficult to find a supplier. I once tried to grow some but the foxes ate it; apparently with no ill-effect.

Have you tried the Bon Maman rhubarb jam that is widely available in French supermarkets? It's very good.
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No haven't tried it and I like rhubarb, we have two clumps of it which gives us enough for tarts and compote but not really enough for making a jam. My wife is a great jam maker and we have a lot of fruit out of the garden so the idea of buying jam is an anathema to her but I will look for some next week and risk her wrath, she allows me to interfere with her marmalade by putting whisky in it though.
 
If you go to the bakers near the fish quay in St Valery en Caux you might be lucky enough to buy one of their delicious rhubarb tarts.

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stevie69p said:
I love how a thread about removing wood stain has turned into one about rhubarb tarts!

:D
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:-)

on the original topic, oxalic acid is certainly worth a try - it is pretty good at getting many stains out. Do bear in mind that, while it is nothing like sulphuric acid, it is somewhat corrosive, so make sure that everything is well rinsed afterwards.
 
maby said:
:-)

on the original topic, oxalic acid is certainly worth a try - it is pretty good at getting many stains out. Do bear in mind that, while it is nothing like sulphuric acid, it is somewhat corrosive, so make sure that everything is well rinsed afterwards.
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Including your hands!
 
The suggestions of various solvents are not without merit but if the stain has permeated the gelcoat they are unlikely to remove it completely. What does intrigue me is this blind faith in oxalic acid and its mystical properties, I do wonder what the basis is.:rolleyes:
 
Fr J Hackett said:
... What does intrigue me is this blind faith in oxalic acid and its mystical properties, I do wonder what the basis is.:rolleyes:
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I'm not sure that "blind faith" is a fair description - it is a recognised cleaner and one of the few things that have much effect on rust stains. It's worth a try, but there is certainly no guaranty that it is going to do the job.
 
Fr J Hackett said:
The suggestions of various solvents are not without merit but if the stain has permeated the gelcoat they are unlikely to remove it completely. What does intrigue me is this blind faith in oxalic acid and its mystical properties, I do wonder what the basis is.:rolleyes:
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I know what you mean about the ‘blind faith’, but …

The stain may contain a mixture of dye and pigment, and many wood dyes for fade resistance are ‘metal complex’ dyes - i.e. dye complexes with transition metal ions such as chromium and cobalt (https://www.popularwoodworking.com/article/making_sense_of_dyes/). So it is possible that oxalic acid’s complexing powers (why it is good with iron stains) might have a beneficial effect by preferentially complexing the metal ion of the dye complex.

But before trying an oxalic acid based cleaner, or if one has proved to be ineffective, I would as you suggest try organic solvents - both alcohol and petroleum distillate-based, as both may be used in the original stain. And as you say, if all those fail I’d next try a mild abrasive - perhaps first a ‘magic eraser’ block? - with repolishing.
 
Ordinary brush cleaner may do the job. It's great for removing mould from upholstery (yes, I know it's not the same but not much else removes mould). Failing that Acetone moves most things or maybe methylated spirit as a less harsh liquid.
 
Fr J Hackett said:
The suggestions of various solvents are not without merit but if the stain has permeated the gelcoat they are unlikely to remove it completely. What does intrigue me is this blind faith in oxalic acid and its mystical properties, I do wonder what the basis is.:rolleyes:
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It isn't a question of blind faith but the result, in my case, of long experience. I have been using it to clean the 53-year old gelcoat on my boat, two or three times a year, for more than 20 years.

Oxalic acid is inexpensive, readily available, reasonably safe to use and very effective.
 
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