Does Varnish Have a Shelf Life?

Little Rascal

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Just came across some International varnish and UCP undercoat in the back of the cupboard. Neither seems to have been opened but they must be around 8-10 years old. Will they still be ok to use?

Jon
 

Norman_E

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The varnish is most likely OK though it may need a good stir, and may have formed a skin on top, which must be removed.

The undercoat will have suffered from its heavier elements settling at the bottom of the tin and becoming pretty solid. Whether it will be possible to mix it all back together is just a matter of experimentation.
 

VicS

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UCP is Universal Clear primer Now discontinued.
I've not used it but I don't think it will have any solids in it to settle.

Both i would expect to be OK if genuinely unopened but if the varnish is the quick drying single pack polyurethane one it may have deteriorated if the can has been opened.

I assume UCP is replaced by
CWSFastDry_750mlkit_EU_5.png
 
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aquaplane

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If you can't steal a wisk off the kitchen mixer I've found a bit of bent wire (coathanger style) the shape of a Westerly Cardinal top mark in a drill stirrs up paint quite well.

When you take the skin of varnish there is always bits in it, not good enough for a perfect finish. I have used some for early coats but got new good stuff when I was fed up of sanding bits off between coats.
 

Croc

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Racking the memory cells UCP was a clear two part very hard polyurathane based primer.... an excellent product... but very unusual. It was an off-spring of another excellent and now discontinued International product....Moisture Cured Polyurathane Varnish. That worked on the same two component principle. There was no mixing of components as with two pot varnish or paint.You just painted it on the wood straight from the can that was one component .The curing agent was moisture in the air and I think a recommendation was if painting in arid conditions boiling a kettle the other side of the room helped the cure and speeded the drying.
It seems unlikely but it was the case...I sold very few cans of the MCPV but UCP was popular.
If the UCP has never been opened it should be fine but if it has you will find a gin clear solid block of plastic in the can.
 

xtiffer

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Racking the memory cells UCP was a clear two part very hard polyurathane based primer.... an excellent product... but very unusual.

No, it was a single pot clear primer that dried very quickly.
Ideal for spars but not recommended for oily wood such as teak.
Great stuff, sorry they don't make it any more.
Cheers,
Chris
 

Croc

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Keep up... I did not say it was not a one can product. I was trying to explain, and obviously failed, that the hardening agent in UPC was the moisture in the air.
The chemistry was completely different to conventional paints and varnishes and was more similar to 2-pot products. Its advantage over other primers was that after it was cured it was completely inert and did not react with virtually any product you applied over it. Its disadvantage was that it was extremely hard when cured and a thick coat could crack if the substrate flexed.
I guess it was another product that was wiped out by the war on VOCs that has changed the nature of the stuff we slap on and taken some excellent materials off the market.
 

Pasarell

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UCP

Croc is right about the UCP. It is a moisture cured urethane that is water white - no pigmentation at all. If unopened there is a good chance moisture has not got at it and it will be OK to use. If it's liquid it is OK, but remember it is really a one shot product at this age. Once stirred you will introduce moisture and start the unstoppable curing process.
Excellent adhesion to wood so ideal as a primer for other varnishes but not good in UV so needs a varnish overcoat to protect it.
Sorry to disagree with VicS but it is about 50% solids made up of the resin, dryers etc. The rest being solvent. If there were no solids it would not form a film.
As for the other varnish it's probably OK to use if unopened and has been stored at reasonable temperatures. Only way to find out is to open it.
 

VicS

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Sorry to disagree with VicS but it is about 50% solids made up of the resin, dryers etc. The rest being solvent. If there were no solids it would not form a film..

Fair enough. I suppose meant undissolved solid, pigment or whatever.

I meant it is like varnish in having no solid content that settles .. none that ive noticed anyway, not like the paint undercoat that was mentioned in a previous post, so stirring will not be the major problem.
 

peterb

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Way back (late seventies?) at the Southampton Boat Show, Calshot Activities Centre were running a competition, which much to my surprise I won. The prize was 5 tins, each 0.66 pints, of International Blue Peter Yacht Varnish.
I used some of the first tin to tidy up a dinghy I used to own, but rather than leave the remainder to skin over I used it to varnish some flush doors in the house. The results were so good that I decided to keep the remainder of the tins to revarnish as necessary.

The fourth tin was used last year. It was just as good as the first. By the time that the last tin is used (by then at least fourty years old), I reckon it should just about see me out.
 
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xtiffer

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Keep up... I did not say it was not a one can product. I was trying to explain, and obviously failed, that the hardening agent in UPC was the moisture in the air.

My apologies. I hadn't finished my early morning coffee so
I guess my concentration faltered. I should have read through your post rather than react to the first line.
Once again, sincere apologies.
Cheers,
Chris
 

bedouin

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In my experience you can take any skin off. If then after stirring it looks about the right colour and consistency then it will be fine.

It seems to me that water based paints last much less well than solvent based ones, often seeming to separate.
 

Croc

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UCP is not a water-based paint....which is the reason I think it is no longer made. It has too many VOCs(Volatile Organic Compounds) that are deemed to be bad for the environment. As I have explained the paint reacts with moisture in the air to harden... and it goes rock hard. From what I remember the wood has to be dry otherwise the paint starts to foam with the excess moisture and it may fall off but certainly the resulting bubbles are very hard work to sand down.
It should not be thinned.
 
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