Varnishing Tips

Little Dorrit

Little Dorrit

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Any tips on avoiding air bubbles when varnishing?

I Have been using International Original Varnish but dont seem to be able to get a finish without tiny air bubbles (or could be tiny particles of dust).

I spoke to International who have been very helpful and supplied me with another tin of varnish (from a different batch) but am still getting tiny specks appearing on drying.

I have tried everything decanting varnish, putting through fine sieve, new thoroughly cleaned brushes, low dust area (conservatory) ...but I am still a little dissapointed.

Am I expecting too much or being really dumb?
 
if they are air bubbles, and there is a big difference in temperature from start to drying, they might be coming from the wood itself if it sealed / varnished on the other parts.

Perhaps try varnishing at the end of the day as the timber cools down ?
 
Thanks Sarabande. The washboards already have about 5 coats on them...so I am sure its not moisture. I have actually come to the conclusion its pollen as there is alot where I live so I am going to try varnishing somewhere else...but any other suggestions would be welcome.
 
paella said:
Thanks Sarabande. The washboards already have about 5 coats on them...so I am sure its not moisture. I have actually come to the conclusion its pollen as there is alot where I live so I am going to try varnishing somewhere else...but any other suggestions would be welcome.
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Screw some gash screws into the end of the washboards. After varnishing, suspend them, upside down, and allow to dry, low and behold, no pollen or dust has settled on them.

I do this with everything I can turn over, including teak and holly floorboards, with excellent results. Have done for years, it works.
 
I was convinced I had tiny air bubbles too, but the wisdom was that it was dust. Proven right by a fit of cleanliness.

Technique I have not tried, but is supposed to be the way. Varnish undercover outdoors on a day when it is raining. The rain washes the dust out of the air. I believe that paint spraying is sometimes done in a special spray booth which has an artifical waterfall to clear dust.
 
Is It possible that you have thoroughly stirred the varnish... as per instructions on tin ...and not allowed it to stand for an hour or so to allow any bubbles to clear?
Just a thought.
 
I have never stirred varnish, that is guaranteed to get bubbles in it. I also found that it is important not to use White Spirit when thinning varnish or cleaning brushes, it is NOT the same as No 1 thinners and causes bubbly effects in the finish.

As already mentioned cleanliness is essential, tack cloths are a must.
 
Another tip.

If you find small particles of dust on your final coat you should 'sand' down very lightly using the reverse side of the sandpaper. It removes dust and does not affect the finished surface.
 
Leighb said:
I have never stirred varnish, that is guaranteed to get bubbles in it. I also found that it is important not to use White Spirit when thinning varnish or cleaning brushes, it is NOT the same as No 1 thinners and causes bubbly effects in the finish.

As already mentioned cleanliness is essential, tack cloths are a must.
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I agree its best not to stir varnish, although you have to if you thin it!

I am surprised to learn that white spirit can cause any problems. The composition of "thinner no1" varies with brand but according to International Yachtpaint can be up to 100% Naphtha (petroleum), hydrodesulfurised heavy, aka white spirit

I find that water and a wet sponge is a good way of getting rid of sanding dust, after brushing and vacuuming, from sealed surfaces.

My main enemy are brushes that are not properly cleaned, or have picked up dust during storage since being cleaned.

I usually try to clean brushes in white spirit followed by brush cleaner followed by detergent ( w'up liquid!) and warm water.
 
Leighb said:
I have never stirred varnish, that is guaranteed to get bubbles in it. I also found that it is important not to use White Spirit when thinning varnish or cleaning brushes, it is NOT the same as No 1 thinners and causes bubbly effects in the finish.

As already mentioned cleanliness is essential, tack cloths are a must.
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always warm the varnish, stand the pot in a paint kettle of hot water before & during use. it thins the varnish without losing body
 
If you are getting air bubbles then it means that the varnish has probably lost its solvent content. The air bubbles are from where the surface skins over before the solvent or carrier has chance to flash off. One option is to add a small amount of white spirit just to slow the coating down or apply very thin coatings and build it up.


If the tin is new then it should be fine but you must stir it before use. I normally turn it upside down for a few mins before i use it.
 
A decent brush should remove most air bubbles. Dust is the biggest issue but a few sessions with a chamois should clear that up fairly soon. Gently stirring shouldn't introduce much air to the varnish. Much less than shaking the tin which is what I usually do.:D And I have the nerve to call myself a professional occasionally.;)

Best thing to do with varnish is not look too closely once it's done. If it looks good from five feet away then that is as much scrutiny as it's ever really going to undergo so it can be called good enough.:D
 
I have the nerve to call myself a professional occasionally.

Best thing to do with varnish is not look too closely once it's done.
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Obviously a professional and "craftsman"

member of the Guild of Master Varnishers too I bet :D
 
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VicS said:
Obviously a professional and "craftsman"

member of the Guild of Master Varnishers too I bet :D
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Absolutely. Truth be told I hate varnishing. But 5 years on classic superyachts has lead to me becoming fairly good at it. What I really hate though is all the BS that is constantly spouted by people who fancy themselves to be experts.

The important thing to remember is that the primary reason for varnishing is to protect the wood. People tend to forget that.
 
Woodlouse said:
The important thing to remember is that the primary reason for varnishing is to protect the wood. People tend to forget that.
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The same as paint.

I have lots of brightwork on Little Ship and I do enjoy doing the varnish (sad I know) but I agree with the comment of "dont look too closely" . when we look at paint or varnish inside or under artificial light, every mark will show. Once outside they all seem to disapper unless you look very closely.

I have a run (looks like a curtain :)) on my transom which up to now nobody has mentioned. I suppose one of the North Wales mob will find it now.

OK.. my tips....... varnish in cool weather or rooms using a good brush, light sand between coats using 240grit, clean the dust off with tack cloth or as I do with white spirits and a clean cloth....use a foam brush for the last coat. It's not rocket science.

Tom
 
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