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Author Topic: Painting over oil based varnish  (Read 691 times)

ukmike

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Painting over oil based varnish
« on: September 05, 2018, 11:34:01 PM »

I need to paint, (white gloss), over an oil based varnish finish using a spray can.
What can you recommend, bearing in mind the possible / probable reaction that cellulose type paints have when applied to enamel paints ?
Thanks.
Mike.









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Brian60

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Re: Painting over oil based varnish
« Reply #1 on: September 06, 2018, 08:17:53 AM »

If you are sure it is an oil based enamel on there and you want to use cellulose, the only recourse will be to first apply a sealing coat between them. Otherwise forget the cellulose and go for an acrylic (water based acrylic not chemical based as are Halfords car paints) paint. Water based acrylics will should cover with no problem.

ukmike

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Re: Painting over oil based varnish
« Reply #2 on: September 06, 2018, 09:51:16 AM »

If you are sure it is an oil based enamel on there and you want to use cellulose, the only recourse will be to first apply a sealing coat between them. Otherwise forget the cellulose and go for an acrylic (water based acrylic not chemical based as are Halfords car paints) paint. Water based acrylics will should cover with no problem.
Thanks for that Brian but I think my question needs some clarification.
Firstly, the varnish on the hull is a modern adaptation of the old Chinese tung oil recipe, ( Le Tonkinois ), which is tung oil with modern driers added, therefore I can only use paints that don't contain things like cellulose, acetones, propane and naptha etc.
Only true Enamels are what I need, of which most so called Enamels are not.
Paints that can be cleaned up using turps or white spirit are usually enamels.
I'm not a lover of water based Acrylics as they tend to be quite hard when dry, a wooden boat needs paint/varnish that is flexible enough not to crack when the wood moves, as it surely will.
So the question remains, does anyone know of a spray can paint that is proper spirit based Enamel ?


Mike.
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nemesis

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Re: Painting over oil based varnish
« Reply #3 on: September 07, 2018, 12:58:23 PM »

You might find that there is no"key" on varnish, you will be able to coat up and cover but give it a knock and it will probably chip. Tried this in my hall before trying to burn the varnish off, gave up and replaced all the skirting. Happy days, nemesis
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Howard

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Re: Painting over oil based varnish
« Reply #4 on: September 07, 2018, 06:02:57 PM »


have a look at a decorators centre for a tin of zinner it might work.
               Regards Howard.
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tonyH

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Re: Painting over oil based varnish
« Reply #5 on: September 07, 2018, 06:28:19 PM »

Zinnser (part of Dulux) and probably the red tin!
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ukmike

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Re: Painting over oil based varnish
« Reply #6 on: September 07, 2018, 07:36:19 PM »

Many thanks for all the info, much appreciated.

Have varnished several test pieces and tried different types of paint on them, including PlastiCoat, Rustoliem and other high end makes, all resulted in virtually instant reaction.
I have been looking for International Japlac but, alas, it was discontinued in 2012. There are a few sellers offering it on eBay but not in white. Wouldn't buy it anyway, as it must be well past its use by date.


I have found success using a relatively cheap brand from Wilko which I happend to have in the shed , no reaction at all with good obliteration and doesn't chip off when dry
Will go with that one I think.


Mike.
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derekwarner

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Re: Painting over oil based varnish
« Reply #7 on: September 07, 2018, 10:38:01 PM »

Mike....it is good that the trial of WILIE paint appears to be sound & stable!......I didn't comment previously as I had no answer or experience suffice to say that the Tung Oil base in the original Le Tonkinois  varnish is the same Tung Oil as used by the Chinese in 400 BC to waterproof their water craft

I understand the original Le Tonkinois  [now also discontinued  <*<] had an amazing property in the depth of penetration soaking in timber

Todays versions appear to be synthised versions of the original ..a little like Shellac........

Derek
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Derek Warner

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ukmike

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Re: Painting over oil based varnish
« Reply #8 on: September 07, 2018, 11:23:35 PM »

Mike....it is good that the trial of WILIE paint appears to be sound & stable!......I didn't comment previously as I had no answer or experience suffice to say that the Tung Oil base in the original Le Tonkinois  varnish is the same Tung Oil as used by the Chinese in 400 BC to waterproof their water craft

I understand the original Le Tonkinois  [now also discontinued  <*< ] had an amazing property in the depth of penetration soaking in timber

Todays versions appear to be synthised versions of the original ..a little like Shellac........

Derek


I thought that Shellac was the main ingredient in French Polish, that and Methylated Spirit of course.
French Polish is quite hard and brittle, unlike Le-Tonkinois which is flexible, allowing the timber to move without cracking. Also, due to the Tung Oil it has outstanding self leveling qualities which obviate the need for much brushing out, as theTung Oil lays on the surface then hardens. Seeing is believing.
I have used many of the, "Premium"brands of varnish but nothing has come close to the finish of Le-Tonk'.
I don't believe thatTung Oil can be synthesized, I hope not anyway. Le-Tonkinois still is pure Tung Oil but with the addition of modern driers. BTW, the original recipe is still available.
Sorry to ramble on about it Derek, but it is without doubt the best, not the cheapest though.
Only my opinion of course.
Mike.

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Andyn

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Re: Painting over oil based varnish
« Reply #9 on: September 08, 2018, 12:19:08 AM »

Have you given the Halfords enamel sprays a go? I tried them for the first time earlier this year, though the safety data sheet gives no indication as to their chemical makeup. Perhaps an email to JBL may yield an answer before spending out on a can...
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RST

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Re: Painting over oil based varnish
« Reply #10 on: September 08, 2018, 12:58:50 AM »

Have you given the Halfords enamel sprays a go? I tried them for the first time earlier this year, though the safety data sheet gives no indication as to their chemical makeup. Perhaps an email to JBL may yield an answer before spending out on a can...

...my experience is to always use Halfords cans for the last 10+ years.  I have, however had some very weird experiences with them over the last 12 months.  Have they changed formulation the past 12 months?  Halfords used to be the bog. std. go-to for paints but now they're almost a write-off for me, even the primer has been utterly crap.  It all "peels" off the surface rather than bonding with it now?

I went out to find a white enamel few weeks ago -I found the wikipedia definition of an "enamel" nowadays but what utter complete tosh.  I can't help you much Im afraid apart from recommend you try bits for compatability.  Having said that have you tried "Johnstones" paints?  I struggled on my parents conservatory -their primer worked .  There's always "international" -I came across an old tin of ther red oxide who I've been using recently because of no reaction with pretty much anything -that said it's an old tin, probably wouldn't help LoL.
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derekwarner

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Re: Painting over oil based varnish
« Reply #11 on: September 08, 2018, 03:15:29 AM »

Shellac flakes are I unserstand a by-product from a resin & dung  O0 from the Lac beetle from Asia

From their WEB site ....it appeared that original Le Tonkinois  [now also discontinued  <*< .....I understand it is still available in a number of marine paint shops in France

There is no Australian stockist listed for Le Tonkinois , however the Australian Feast Watson market Tung Oil, but only in a matt finish
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Derek Warner

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