Wipe on Polyurethane Varnish

[Andyjr1515]

Hi

In my single-cut bass thread, I mention my usual method of gloss-finishing my basses and guitars, which is wiping on.  I recently did a thread on another forum, so forgive me for cutting and pasting, but it is a technique that is probably of interest to any of those of you who might be stuck for facilities or equipment but still want to produce an acceptable (but not perfect....of which more later) finish.

But before I start, just a few of the common-sense health and safety precautions: use varnish and thinners in accordance with manufacturers recommendations, especially relating to decent ventilation, skin contact, flammability, etc . Be aware that cloths soaked in thinned varnish can present a particular fire risk (including spontaneous combustion in the right circumstances).  Once used, let them dry flat and preferably outside.

The products illustrated are using the UK terminology, but the materials are general household products found in most DIY or Decorators retail outlets.

I use a wipe-on technique for varnishing, using standard old-fashioned household polyurethane varnish. I don't have anywhere satisfactory indoors to spray either cans or spray-guns and needed to find a method that I could in in a spare room rather than having to wait for a dry, still, insect and pollen-free day everytime I wanted to finish a bass or guitar (a long, long wait often in the UK!)

There are a few plus's and minus's:

• It will never look quite the same as a well applied and properly buffed spray finish
• It isn't as tough as a commercial poly finish - but it is tough!
• You can put a couple of coats on per day (One 1st thing in the morning and one in the early evening)
• For a wood or veneer finish it produces a very acceptable result
• For a plain colour (just done one in the finisher's nightmare - gloss black), it takes a number of tips and tricks to get it OK (but refer back to point 1!)
• There are some important differences - the main being that you DO NOT buff to a final finish....in fact you CAN NOT buff to a final finish. The technique is different because the chemistry is different. More on this later..

The kit I use is simple:

Ronseal Hardglaze or Rustins Clear Polyurethane gloss varnish; White Spirits (I think this is referred to as clear mineral spirits in other countries?) to thin it; hence the jam jar; rubber glove; cheap, disposable microfibre cloths. I am still using the original 'high volatiles' varnishes - simply because I haven't experimented enough with some of the more modern low volatiles ones. That's a summer project for me...

I'm sure you have, but if you haven't yet discovered micro-fibre cloths, it's worth doing so. They are:

• Generally dirt cheap (except the specialist ones, see below) I think these were just a few £ in the cleaning goods section of a local supermarket.
• COMPLETELY dust free and lint free - but never cut them otherwise there's bits everywhere
• Soft and fluffy, very absorbent for the varnish

I use one more type of micro-fibre cloth, a particular type, as the best 'tack rag' I've ever used. It's a window-cleaning cloth and I think it cost about £6 ($10). My dust bugs issues have vanished since going from decorators sticky tack rags to this:

The technique is simple:

• thin varnish with about 30% white spirits
• don rubber glove
• wipe over surface with micro-fibre 'tack rag'
• take corner of cheapo micro-fibre cloth
• dip in thinned varnish, squeeze out excess
• wipe on

This is a heavily figured veneered top after about 5 coats (over 2 days)...note that I'm doing it over a CARPET!! Actually, I forgot to put the newspaper down but got away with it. It only drips if you major-ly overcharge the cloth:

 

Although I said above that it's not the best way for a plain sprayed colour, it still isn't terrible...a guy from one of the UK forums persuaded me (under duress and suitable cautionary words to manage expectations) to do him a gloss black body...the most challenging of any colours:

There are some important tips and tricks, like with everything. I'm sure there are others, but these come to mind:

• Wipe with a good quality 'tack rag' (see above for my recommendation) to ensure the surface is dust free. Try to keep dust to a minimum! Remember spray finishes dry within seconds...this takes an hour or so and plenty of time for the dust buggies to land and sink in
• Apply multiple thin coats. Maximum 2 per day (one in morning and one in evening)
• Flatten with 1000 grit, used wet, every 6 or so coats
• After 5-6 days, there should be sufficient thickness. Let it cure for at least 3 -5 days
• Flatten with 1000 grit used wet (if necessary) and finish with 2000 grit used wet
• Ensure varnish is properly thinned...maybe go up to 40% thinners at this stage. Dip the microfibre in the varnish and squeeze it almost all out then apply a VERY light coat. Let it dry. Apply a second VERY light coat and, if necessary a third.
• Don't buff - nitro coats 'melt' into previously applied coats. Poly applied like this doesn't do this so buffing will simply wear away the shiny top coat and expose the sanded under coat
• Leave at least 1 week (2 is better) then polish with good quality, low abrasion auto polish (Macguiers Ultra is a good one)

Hope this helps - if you try the approach let's see how you get on and don't hesitate to contact me

Oh - and by the way, it was this present camphor and alder build in Build Diaries that sparked off the interest:

 Not bad for a pot of household varnish and a cheap rag done in the spare bedroom? 

Andy

 

 

[Prostheta]

Fantastic tutorial Andy. Very useful and practical information.

[Andyjr1515]

Thanks, Prostheta ! 

[GuitarMaestro]

Really well written and great tutorial Andy! Thanks alot for taking the time!

You write about the wipe-on poly:

• It will never look quite the same as a well applied and properly buffed spray finish
• It isn't as tough as a commercial poly finish - but it is tough!

 

How would you say it compares to a SprayCan 2K poly finish? When you say it will never look quite the same than a sprayed finish - what are the main differences?

[Andyjr1515]

1 hour ago, GuitarMaestro said:

Really well written and great tutorial Andy! Thanks alot for taking the time!

You write about the wipe-on poly:

• It will never look quite the same as a well applied and properly buffed spray finish
• It isn't as tough as a commercial poly finish - but it is tough!

 

How would you say it compares to a SprayCan 2K poly finish? When you say it will never look quite the same than a sprayed finish - what are the main differences?

Hi, @GuitarMaestro 

Thanks!

I've not used the 2K poly so am not sure how it would compare.  

My comment is really to make sure that people don't do this and expect it to be the same thick, solid and flawless finish as many of the guitars they would pick off the walls of their local guitar shop.  I do think it compares well with many spray-can home jobs (and certainly MUCH cheaper) but even here, not with a can-sprayed nitro formulation.

The reason is that, for nitro, each coat melts into the previous layer,  Then you can do the time honoured method of sanding and buffing down to the perfect shine.  Poly wiped on (and I presume sprayed on too...anyone know?) doesn't work like that.  Each coat is a separate coat,  After the final 'shiny' coat, if you buff hard, you wear away the thin top coat and hit the duller (and probably finish-sanded) under layer. 

[GuitarMaestro]

Thanks for your answers.

Concerning spraying poly - it seems it can be done in a similar way than nitro:

Jeremy sprays about 10+ coats and sands in between. I don't know if the individual layers melt together (probably not) but Jeremy at least does not warn about sanding/buffing through the top coat...

 

 

[Andyjr1515]

2 hours ago, GuitarMaestro said:

Thanks for your answers.

Concerning spraying poly - it seems it can be done in a similar way than nitro:

Jeremy sprays about 10+ coats and sands in between. I don't know if the individual layers melt together (probably not) but Jeremy at least does not warn about sanding/buffing through the top coat...

 

 

That's interesting.  It might be that the top coat is thick enough to take a major buff without cutting through.  With hand wiping, you get the previous coats completely flattened and level and then the final gloss on top is very thin indeed.  Still pretty tough, though.  I've personally never had wear through regular gigging....

[GuitarMaestro]

Durability sounds good then!

Concerning  spraying poly i found several tutorials stating the following:

If you want to apply several coats and you want them to bond chemically and not mechanically, the timespan between coats has to be short (10-15 minutes for the Spraymax 2K for example). Most of them spray several coats in short succession and then they wait, sand and then apply several coats again, etc.

Might be possible with wipe-on as well?

 

 

[Andyjr1515]

16 minutes ago, GuitarMaestro said:

Durability sounds good then!

Concerning  spraying poly i found several tutorials stating the following:

If you want to apply several coats and you want them to bond chemically and not mechanically, the timespan between coats has to be short (10-15 minutes for the Spraymax 2K for example). Most of them spray several coats in short succession and then they wait, sand and then apply several coats again, etc.

Might be possible with wipe-on as well?

 

 

OK - that makes sense and probably explains why you can generally buff modern professionally sprayed poly finishes.

Not possible with wipe-on, I'm afraid.  The flat surface is created by the self-levelling of the thinned varnish.  If you tried to recoat the setting first coat, you would just end up with wipe marks and ripples.  

With spray, the droplets are hitting the surface and immediately spreading.  You do, of course, end up with a bobbly surface but this can then be flattened and buffed because of the above explanation you've posted. 

 

[GuitarMaestro]

Makes sense - good to know that this is not an option with the wipe-on.

[Borester]

I know this guide was posted a good few years ago so apologies for my late comment!

This guide has helped me so much, where i live there is nowhere that sells Nitro rattle cans so this post has saved me in the region of £60 quid and seems so simple to do! 

 

If my project turns out half as good as yours I'll be pleased so thanks for the tutorial!