Achieving a really high gloss

Flip

I'm coming to the end of my first kit build guitar and although it's too soon to know if it's halfway decent I'm enthused enough to want to try again. The only decision I've made is not to buy a kit with a veneered body. Most of my doubts about my first try centre on the veneered body.

Instead, I'm considering a solid ash-bodied bass but I'd like to get the sort of really high glass finish I typically see on PRS instruments. May I seek advice here?

I've used several coats of stain (obviously not necessary on the bass) followed by two coats of Boiled Linseed oil. On this, I've applied six coats of very thin 4-1 white spirit/polyurethane gloss, followed by two or three coats of the same mix but with the ratio switched, 4 gloss to 1 white spirit. I still don't seem to have achieved that almost wet, glassy finish.

Is the key to use a grain filler?

Are there any other suggestions?

HilditchGuitars

Grain filler definitely on something like Ash. Also, you're going to need to flat sand and polish/buff to get the really shiny wet look.

Flip

Many thanks - I'm just finishing my first build so well past the stage of grain filling but the body only had a very thin veneer so it might have been difficult anyway.

The next project's a bass guitar and unfortunately, I could only get a mahogany body, ash is out of stock. Debating whether to grain fill and gloss finish or just sand then stain a little and finish with a satin poly - aiming to get a finish rather like the new model Fender guitars. 

Thanks, your help appreciated anyway.

HilditchGuitars

Flip said:

Many thanks - I'm just finishing my first build so well past the stage of grain filling but the body only had a very thin veneer so it might have been difficult anyway.

The next project's a bass guitar and unfortunately, I could only get a mahogany body, ash is out of stock. Debating whether to grain fill and gloss finish or just sand then stain a little and finish with a satin poly - aiming to get a finish rather like the new model Fender guitars. 

Thanks, your help appreciated anyway.

Nothing unfortunate about mahogany, I think it's a beautiful wood. What is unfortunate is the fact I have a great lump of ash sat outside waiting to be milled in spring. I could have sent you some if it was ready. It can look nice in satin too, a bit like the Warwick basses. 
Good luck, whatever you decide, I'll be on standby if you want anymore guidance 

Andyjr1515

Flip said:

I've used several coats of stain (obviously not necessary on the bass) followed by two coats of Boiled Linseed oil. On this, I've applied six coats of very thin 4-1 white spirit/polyurethane gloss, followed by two or three coats of the same mix but with the ratio switched, 4 gloss to 1 white spirit. I still don't seem to have achieved that almost wet, glassy finish.

This is presumably on the first kit-built?  Do you have a photo of how it is at the moment?

The simple answer - but it depends (see below) is that you don't yet have enough coats of polyurethane.  So you are still filling the grain with varnish but - especially thinned - the dried varnish is very, very thin and so it follows every tiny 'hill and hollow' of the grain. 

It IS possible to get a pretty decent non-spray gloss finish with polyurethane, but it does take a few tips and tricks.  But it will be 'fit for purpose' rather than 'flawless under close examination' even with those tips and tricks. And with polyurethane, you can't 'flatten and buff' as you would with, say, a nitro sprayed finish.

I use Ronseal Hardglaze polyurethane for all of my gloss finishes (if you are after satin, by the way, there are some great products we can point in your direction) and wiped or brushed on.  This is on unstained timber:



And this is on stained maple:


One was wiped on.  One was brushed on.  Neither were grain-filled.
 

But a few questions first to work out where you are starting from:

- How are you applying the varnish?

- What varnish are you using ?

- What stain did you use?

- How long did you leave the boiled linseed to dry before applying the first coat of varnish?

- Do you have a photo of the present progress?

Flip

First my compliments on your achievement, I'd be happy to get either of those results. I sanded i9n stages from 180 to 1200.

Second to answer your questions:

All coats wiped on with a lint-free cloth.

I've used Barrettine polyurethane gloss.

I used Crimson Guitars' water-based stains, two coats thin black, second around edge only, both rubbed down, then six thin coats of royal blue. Half a day between coats with sanding before next coat. I mentioned boiled linseed oil because that's what I intend to use next time - I used an expensive Crimson product which seems to be essentially BLO. Day drying before oil though on the front I made a mistake and forgot the oil so that went on over one thin coat of 4:1 white spirit:varnish mix. One day drying between each of six coats and rub back. Finally, topcoats of 1:4 white spirit:varnish mix, None on the neck, two on back and sides, three on top of the body. That's where I am now. When I judge body topcoats hard enough I propose to use a buffing wheel and compound to finish and possibly a final polish. I had a luthier do the frets and he complimented me on the neck finish with just think coats so I left it at that. 

Sorry, I don't know how to attach a photo. I've pasted location on computer but it doesn't show

Flip

Since writing the above I've checked the FAQ and don't have any of the picture hosting options. You can see the present state if you look on my blog at kitguitarbuilder.blogspot.com.

Jazzthat

I am not as much experienced as others on this forum , but I can sprayed my project guitar and sanded it from 400 to 7000 by hands .
This took bloody long time and in the end there was no gloss I hoped for ( just like you probably at the moment ) .

Then I purchased dedicated 3 stage Rupes compounds and their dedicated small pads ( 40mm , very handy to move around on curves etc ) .
After this , the gloss popped up like a dream . Though I mocked up early stages and that also showed up as a result .

Flip

Very impressive results jazzthat. You can see what I've achieved so far on my blog, Day 11. Your choice is evidently to remove all trace of the original wood and the gloss is excellent. I'm trying to get a coloured but transparent result so the flame maple shows through - the veneer is very thin so the degree of sanding possible is quite limited. The effect I'm seeking to emulate is that found most often on PRS instruments. Of course, I realise they're professional but that's the target.

Flip

Interesting that you've stain side the voids; did you line the,m with copper tape afterwards?

Jazzthat

Thanks @Flip ; . 

There wasn't much to show tbh as it was a 5 piece alder body , so I went for solid colour .

There's of course a limitation of what we can achieve in home DIY ( garden ,shed etc ) environment .

After I've sprayed top coat and sanded it up to 7000  ( with poor results ) , i had rang professional car paint body ( the guy did respray on my car bumper ) and had  asked him how to get real high gloss .
He  advised to spray about 10 light coats and 2 heavy after that .
The rest is machine polish and choice of professional products to help achieve desired results .
I have only used ordinary drill , and those Rupes polishing compounds did the rest . 

And yeah ,pickups and all other cavities are now covered with copper tape

Andyjr1515

 Hi
Easiest way of posting pictures is probably Imgur.  It's free and pretty efficient.  Most folks are a bit wary of following external links...

But I did - and your build and finishing is looking very good so far.   

So from what I understand, you have been using the linseed oil effectively as a sealer?

You can use the poly to seal too so don't worry about the fact that you missed that step with the top.  But the wood is thirsty and will tend to absorb the initial coats quite a lot.  But it will get to the same stage after enough coats.

Personally, I wouldn't use that much thinner (assume you are using white spirits?) in the mix - and particularly for the initial coats.

So - the approach I've found most successful using the kind of products you are and with a stained wood finish:

For a stained top, then when you get to the point of flattening, you need to be flattening the varnish and not the stained wood.  Therefore you need a decent number of coats before you do that otherwise you will very quickly cut through the varnish into the stained wood, and the stain will then sand away very quickly.

So more coats and thicker at first.  For highly thinned coats, I'm talking maybe 20 or so!  But for, say, 10% thinners, then still at least 5.
  
Once you have a workable thickness, then you can start flattening between every 2 or three coats.  Yes - 1500 grit to maybe 2500 is OK - used wet and with a block, and wiping the slurry off as you go.  Here you are getting rid of runs, dust buggies and also the peaks of any ripples.  And remember, you are flattening the varnish, and not getting anywhere near the stained wood.  Now you have a decent thickness of varnish, you can afford to thin a little more (around 30%) because this will produce less ripples.

When it is starting to get to where you want it, you need to do the final flattening and the final couple of wipe-coats.  Use 2500 grit - no coarser - to do the flattening.  And now you can thin probably 50%.  You want to do a quick thin 'final' coat.  In reality, it won't be quite the final because you will probably find when it is fully dry, that some of the matt from your levelling is showing through.  DON'T flatten again.  When dry, just give it a second (and sometimes a third) 'final' 50% thinned wipe.  You might need to repeat this whole set of final steps a couple of times.  If there are aberrations, then flatten them out with the 2500 and do the final 2 or three 50% thinned coats again.

Then leave it at least 2 weeks to fully harden.  Then hand polish with Meguiers Ultimate Compound.  You want to shine the very top of those final 2 or 3 VERY thin coats.  T-cut will cut right through.  A drill buffer will melt right through.


And that leads to the most important difference between multi-coat polyurethane and, say, nitro.  Each coat of nitro melts into the previous layer and becomes one homogeneous thickness.  So here you can buff down through the merged layers to a shine.

Standard polyurethane varnish like you are using, however, emphatically does NOT do this. 

Each layer with this type of polyurethane varnish is a separate layer - think slate.  So if you buff here you will very quickly expose the previous layers and will either end up matt - having cut into layer you have previously flattened - or contours with the edges of each layer visible like an OS Ranger map  

With this type of the finish, the build up and flattening is all about getting a perfect base, not the shine...and the shine comes from those last 2-3 thinned and unflattened coats.

Hope this helps!

 
 

Flip

Thanks for your excellent advice. I listen and read everything - perhaps the only problem is that ultimately it tends to cancel each other out eg the reason I started with very thin was the advice of a builder on the channel of the kit maker - almost exactly the advice you've given. That's not ingratitude and I'm grateful and eager to learn but it's the same with the actual stuff. For everyone who recommends Tru Oil there's one who says something else. About the only consistence is that anything other than nitro/poly will need re-doing in time. My build is ultimately for a grandson so durability is paramount. Your work is superb and the one thing I can emulate is to apply a few thinned coats and leave them unflattened.