Mini-Roller causing bubbles in varnish finish - Why?

[EnorMouse]

I am applying a top quality satin finish varnish to some pine & MDF shelving using a quality gloss foam mini-roller, which says it is suitable for solvent based finishes. As I apply the varnish, bubbles appear on the surface and some marking remains when the varnish dries.

I sanded back the first coat, but the problem has reappeared on the second coat, so it is nothing to do with the materials I am varnishing.

Can anyone tell me what I am doing wrong?

Many Thanks

EM

 

[misterhelpful]

You say top quality varnish, but is it solvent based? If not, that could be your problem as foam rollers are not good for water-based finishes. Most varnishes will recommend a brush rather than a roller so double check the tin to see.

However, the cause of bubbles is usually rolling too fast which seems to trap the air from within the foam under the surface of the varnish. See if rolling slowly helps.

 

[EnorMouse]

Hi misterhelpful

Its a standard Ronseal requiring white spirits/brush cleaner to clean up (although I tend to chuck the rollers) so it is solvent based.

I am going to sand down and apply another coat this afternoon, so will try working slower. Will let you know the results.

EM

 

[Nige F]

I think I`d change foam for fleece one

 

[EnorMouse]

@misterhelpful

Can now report that speed and pressure applied seem to make no difference to the problem.

@Nige F

All of the locally available 'Gloss' ones seem to be foam and as far as I can tell, foam of the same density. The fleece ones all call themselves 'Emulsion'.

I seem to recall some time ago having some mini roller sleeves which had a very short straight pile on them, more like a paint pad, but I used them all up (my bad habit of finding them easier to chuck than clean) and can not find any more.

I have ordered some fleece gloss ones off the internet and now wait to see when they turn up. I will keep going with the foam ones and sanding back, to build up a good base and hopefully the new ones will turn up in time for the final coat.

It's either that or go back to the brush, but I do not know what it is about the way that I apply it with a brush, but I always seem to end up with visible brush marks, rather than the perfectly smooth finish that I always hope for.

EM

 

[misterhelpful]

Sorry it didn't work!

I was going to suggest trying a paint pad as they should spread the varnish out thinly but more evenly. As you have managed to order some very short pile mini rollers, which should do a similar job, it will be interesting to know if they work.

I always use brushes for varnishing and agree that you never get that perfectly smooth finish, even with P/U. I personally think that varnish just 'ain't what it used to be'.

I think Nige F was joking about the fleece, hence the wink!! Could be worth a try though.

 

[xr4x4]

Get a decent roller, I've never gone back to foam rollers.

 

[EnorMouse]

The unit that I am working on is a fairly small DVD shelf unit with four of the shelves being glass, so there is only the two sides, top and base and MDF backboard. For some time I have been putting off work on two much larger bookcase units and would like to sort out the varnish problem before I start work on them. Thus I am happy to use my existing project as a test bed. Lets hope I manage to reach a satisfactory conclusion.

@misterhelpful

I was sceptical, but when I found someone advertising a gloss fleece roller I thought that I would give it a try.

@xr4x4

Following on from my last post, I actually searched for "short pile gloss rollers", rather than just "gloss mini rollers" and found a selection of them at www.decoratingdirect.co.uk. I have ordered three different ones to try out and will report back.

EM

 

[opps]

The best quality (and widest selection of) mini roller sleeves are the US brand Wooster. Unfortunately the sleeves are not compatible with other frames.

With regard to pads- ALL of the pads in this country are sh!te. The only decent ones are the Anza pads (from Sweden) Sadly although Anza own Hamilton Acorn the latter refuse to sell them as they have their own crap ones...

 

[mac2or3]

When using solvent based finishes with a foam roller you nearly always get very fine bubbles appearing . I usually apply the finish with the roller then very lightly lay off with a brush thus avoiding brush marks .

 

[Nige F]

Sorry it didn't work!

I was going to suggest trying a paint pad as they should spread the varnish out thinly but more evenly. As you have managed to order some very short pile mini rollers, which should do a similar job, it will be interesting to know if they work.

I always use brushes for varnishing and agree that you never get that perfectly smooth finish, even with P/U. I personally think that varnish just 'ain't what it used to be'.

I think Nige F was joking about the fleece, hence the wink!! Could be worth a try though.

No, I meant pile - as the OP suggested not fleece . Unusual for me I got my words mixed