The latest lacquer drop-fills have had a week to cure. They’ve shrunk back much more than the sanding sealer drop-fills did. In fact – they’re really hard to pick up, and difficult to photograph. You can only really spot them by looking into a light source. That said – you can still pick up a distinct change of level with your fingertip – so they’ll need to be levelled carefully, to begin to blend them into the surrounding lacquer.
The process is much the same as with the sanding sealer dropfills. I strike a razor blade along the corner of a cast iron flat edge, to turn the edge over and create a tiny shave. Instead of masking tape – this time I use Sellotape to mask off the edges of the blade. The Sellotape is much thinner than the masking tape, and so the razor edge is down, almost at the level of the lacquer dropfills, Just a fraction of a millimeter above the level of the surrounding lacquer.
I need to make sure I hunt down all of the drop-filled areas. I really should have counted, and made a note somewhere. Gradually however, I locate each, slightly raised blister, and begin to pare away at the lacquer. The clearance on the blade is minimal – so even the slightest deflection causes scratching to the surrounding lacquer. But by going slowly, keeping the blade as straight as possible, and by changing my direction of attack – the blisters are gradually scraped away, and the little plaques are reduced. This is confirmed by feeling over the areas with my fingertips as a final check. Once it becomes difficult to feel the imperfections at all – it’s time to stop and move onto another area. Eventually, I think I’ve located and levelled all of the raised plaques.
On close inspection – most of the drop-fills now appear to be smooth over the pin-hole areas. I’m hoping they’ve done the job this time. There are a couple where the dropfills themselves, appear to have developed pin-holes of their own. Perhaps these areas had really deep pin-holes originally? Or perhaps the drop-fills were too big, and had problems out-gassing? The problem of pin-holes is also common when gessoing wood prior to gilding. Gesso is a kind of liquid plaster, mixed with glue – and as it dries, pin-holes can develop where bubbles are trapped in the quickly-drying matrix. Obviously – they are a real problem in gilding, since they telegraph through the thin gold leaf covering. They are also, often signs of where the gesso is weak. Since part of the gessoing process involves burnishing the dried plaster finish – pin-holes need to be fixed, (or ideally avoided altogther!), before gilding and finishing.
So, I’m presuming that pin-holes in lacquer may also indicate a potential weakness in the lacquer matrix. I don’t want to leave faults which might result in the finish easily flaking, or chipping off. First signs from the latest drop-fills look favourable – but I may have to revisit a couple of areas again. It would be easy to pass on a few imperfections for the sake of just being able to get on with the build – but I want to try and make sure it’s as good a job as I can do.
With the drop-fills reduced – it’s time to flat sand again. I’m using 320 grit again, and a light touch. With a little naptha as lubricant, and making sure I keep the grit paper clean of clogs – I slowly work across the body, using a cork backing block to exert a light, even pressure. My backing block has slightly rounded corners – this means that the edges of the block don’t tend to drag and cause divots or witness marks. Working into the light again, I use a circular motion to gradually and evenly work across the face of the guitar body – letting the grit on the paper do most of the work. In the image above – you can see how the sanded area towards the camera begins to take on a consistent, matte sheen, The unsanded area beyond, still looks shiny and lustrous.
You can also see a few, persistent low spots around the edges of some of the painted design. Here – level changes are still evident, and where the grit paper has passed over the low spots, shiny lacquer is left. Once the whole piece has been evenly worked over – I return to these areas, one by one and assess the direction and nature of each. I can then begin to work with a smaller backing block, to begin to try and gently feather-in the edges around the low spots. Once the shiny lacquer begins to blend in, I can go over a slightly wider area with the larger, cork backing block – to feather-in the finish more generally. There are one or two particularly stubborn areas, and these require special attention. By now, there is plenty of lacquer on the face of the guitar, and it’s possible to carefully work the surface until all of the low spots appear to be levelled. A final, light pass, with the cork block and fresh 320 grit, leaves an even looking surface, with a consistent, all-over matte sheen – and with no sign of low spots.
Since there’s been a considerable build up of lacquer on the face of the guitar, I manually run a diamond edge burr, to work away at the edges of the bridge screw holes a little. I’m not interested in actually countersinking the holes at this stage – I just want to start to get an idea of how much lacquer has built up, and how glassy the face actually is. Things don’t seem too delicate, and there’s minimal sign of the burr causing the lacquer to shatter around the holes – so I’m taking that as a sign that subsequent drilling might not be too problematic. Hopefully, I can now round off the clearcoating process with just a couple of light applications.
Of course – it all depends on those drop-fills – but as well as applying finishing coats to the face of the guitar, this time I want to include the sides and back of the guitar. I need to make sure the whole body well coated, to have enough coverage to work with during the polishing process.
I clean the whole body down with naptha, and a paper towel – making sure there’s absolutely no powdered lacquer hiding anywhere in the recesses, or spilling over, down the guitar sides. Then, after masking off the neck pocket again – I attach my painting stick, so that I can manipulate the body and get good coverage on the edges, and in all the difficult nooks and crannies.
To keep the final lacquer as smooth as possible, I’ll spray the final coats with the body laid flat. The first application is to the newly levelled face. Once again, I build up full coats with a number of passes, leave to cure for an hour, and then rotate the body and repeat. After three coats, I repeat the process for the guitar sides – hanging the guitar to dry, in-between coats. Finally, I lay the guitar down again supported on a soft bean bag – and lay down three coats on the back of the guitar. (After making sure the grommet holes on the rear are temporarily plugged).
With the guitar body now fully coated, it’s left to dry and cure. A brief check over shows that most of the drop-fills appear to have been sealed – although you can still, just about, make out where they are. I’m hoping that the lacquer will shrink back and even everything out, and that the previous pin-holes will not re-appear – but there’s no way of knowing at this stage. So – it’s another week in the drying cupboard – and I’ll have to wait and see.
Bulletin: 14th June 2019
The latest lacquer has had a few days to cure. I can just about make out the locations of the previous drop-fills, but they’re hard to find, and I can only just spot them when looking into the light. They show as slightly pronounced rings – almost as if there’s a subtle difference in the refracted light passing through the lacquer – rather than anything physical. I think they’ll polish out with one more levelling, although I’d be wise to give them plenty of time to cure and settle before I think about polishing.
There is, however, still one really troublesome pinhole which still hasn’t filled. It’s right on the upper bout and, although it too can only really be picked up when the light is just so – it’s all too noticeable, and I need to sort it before I can finally prep this body for polishing. I don’t want to have to repeat entire coats of lacquer just for the sake of one, solitary pinhole – so I’ll try and settle it using a localised, sanding sealer drop-fill. In my previous tests, these seem to have had a bit more “filling power” than the lacquer drop-fills.
I use a thin bit of wire to act as a dropper. I mask the surrounding area off, and apply a single drop of Mylands Lacacote Sanding Sealer – trying to centre it right on the target. After a few minutes, the centre of the droplet has sunk back as the solvents evaporate away. Hopefully – there’s enough “solid” settling into the pinhole to fill the indentation this time. I’ll have to scrape the surface residue away and feather the fill into the area of the upper bout, before I can see if it’s worked. It may need another application, and I’ll have to resolve this problem area before I can move on with polishing the whole body.