Prepping, grain filling and sealing an Ash Telecaster body.

The “Dragoncaster” body by Phil at guitarbuild.co.uk has finally arrived. The blank I selected was one of three on offer, and I was able to use Photoshop to mock up exactly what I was looking for, and communicate that to the guys who were operating the CNC cutter. The routs and bridge screw pilot holes look well cut and, importantly, match up to the Fender Vintage bridge plate I have sourced. Although Jimmy Page used the toploader holes drilled in the bridge plate, the original guitar had through-body stringing – and it’s good to see that all the string holes match up to my bridge plate, perfectly.

20190320_092441

A closer inspection confirms the quality of the finish. Everything looks flat and evenly sanded, and I can’t find too many faults at the edges of the cutouts. Certainly, none that will be visible when the control and scratch plates are in place. The edges of the body look well rounded – with no dints or flat spots. The only small faults I can find at all, are down in the exposed end grain, close to the jack plug outlet – and they look minor. Not too deep – it looks like they’ll easily fill with grain filler, and sand out.

Although the wood looks well finished, I like to make sure the grain has been raised – especially with Ash, and especially if I’m not sure what effect subsequent finishes might have on any piece of wood. Normally, if you wet a piece of finished, but pourous timber – the grain swells and pushes out slightly. This roughens up the finish again – so although a piece of timber might look to have sanded smooth – some of the grain may have been just pushed over and flattened – rather than having been cut away and removed entirely. The secret to super smooth finished wood is to damp it over, and finish it with finer grades of grit paper – but after having raised the grain first.

If I was planning on using a water based grain filler – I would have raised the grain by using a little wipe over with distilled water. However – with all the routs cut, and with holes drilled through the body, it’s important to try and keep any ingress of moisture, to the heart of the wood, within reasonable limits. You really don’t want to start pouring water down into the heartwood of the body. I’ll be using a spirit based filler, and then a shellac based sanding sealer – so I’ll raise the grain with a wipe over with naptha, instead of water.

20190320_095701

The naptha raises any grain that hasn’t already been sanded off. It also darkens the wood and begins to show the natural colour of the wood, and what it might look like after it has been finished. It will be useful to compare this against the original guitar. It’s possible I may have to slightly colour the wood to match – unfinished ash can be quite lacking in the aged orange/honey tones I’ll be looking for – so I need to look into how I can subtly tone the wood, if I choose to do so. The naptha evaporates quite quickly, and doesn’t appear to raise the grain much – so I’m pleased to conclude that it’s already well finished – but a double check won’t hurt anyway. Using a grey Scothbrite pad over a sanding block, I work across the grain – scrubbing quite hard – but careful to keep the pad flat, and not to introduce any divots. Checking the pad over shows a very slight amount of material removed – but probably just enough to warrant this part of the process. Once I work over both sides of the body, and then the edges – I run over the whole blank with 320 grit, again over a backing block. This time however with the grain. This quickly restores a silky smooth finish to the body. It’s important to work consistently across all of the surfaces – and special care needs to be taken around the upper bout cutouts – which can easily be overlooked.

Although little material was, in this case, removed by raising the grain – a good, close inspection of the surface at this stage always helps to, “get to know” the piece of wood at hand. It always helps to focus-in, and assess the character and individual finishing requirements. With this project, a couple of areas show up as requiring particular attention, when it comes to grain filling – especially a small area at the bottom of the lower bout, just under the control plate. This has a slight burl to the figuring, and will require some careful, fine filling. However it is on an area which will carry the painted design, and so it won’t normally be visible – providing, of course, that it’s well filled and sealed. Another, small dark freckle on the rear of the “hump” on the upper bout needs filling. It will still be visible – but I have been able to ensure it’s, at least, only visible on the back of the body. Other than that – the only other areas which will need attention, are areas such as the one in the image below, where some end grain emerges at the surface. Ares such as the,se should be dealt with by an application of grain filler.

20190320_102029

Ash is quite a porous wood. Largely – it’s that porous character which makes it an ideal choice for guitar building. All those pores and micro-tubes help to establish a musical and resonant piece of tone wood.  However – they will conspire to ruin a fine finish. Paint and lacquer is absorbed into the wood and, where there are open pores, the finish will be literally pulled into the wood – resulting in pin-holes and other blemishes affecting a flat, consistent finish. The image above shows a typical example,where the grain is especially pronounced. It’s possible that marks like these could, eventually, be filled by numerous, subsequent layers of lacquer – but since lacquer tends to shrink back over time, it can take a lot of very expensive clearcoat, and numerous passes with fine grit papers to properly fill marks like these – especially in woods like ash, oak and mahogany. Even then, the marks may emerge months and even years later as the lacquer finish continues to shrink back. In these cases – proper preparation can help reduce the number of subsequent lacquer coats required, by properly smoothing the surface beforehand. That’s where grain filler comes in.

20190325_095616

In this case, I’m using Rustin’s Grain Filler – which is a spirit based, specialist grain filler. It’s kind of a cross between a conventional, resin based wood filler and a very runny putty. It acts a little like gesso – which is a traditional, bonding and smoothing filler used on wood before gilding. With gesso, it’s possible to build up a surface which completely fills imperfections, and builds up a coat which can be subsequently finished to a very high level. In the case of gesso – that coat can be sanded and burnished to such a degree that the thin gold leaf, which is applied afterwards, can be polished to a perfect mirror shine. A finish which is almost liquid in it’s character. With gesso, the actual filler is a very fine whiting powder, almost like Plaster of Paris. Obviously – this gives gesso an opaque white finish – useless in cases where the wood finish needs to show through. That’s where grain filler comes in. With grain filler, the carrier is a spirit based drying oil which carries a finely ground solid in suspension. This solid can be coloured for use on different kinds of wood – in this case, a natural tone to work with the ash. The spirit based carrier is absorbed by the wood and pulls the fine filler into the pores of the wood as it does so. As the carrier hardens, the filler is fixed in place, and bonds to the wood. It’s a very fine filler – so it penetrates all the pores and blemishes in the wood, but it leaves the majority of the internal wood structure with the same porosity – merely sealing the outside few millimetres of the guitar body.

The grain filler as supplied is quite thick, and needs letting down with white spirit, until it’s the same consistency as double cream. It can then be worked into the surface of the wood using a rag or a squeegee. Importantly, the filler is worked into the surface of the wood by applying it and working, with the grain. This forces the filler into the open pores of the wood. It helps to physically force it in as much as possible, so I push quite hard with the squeegee, but it’s equally important not to leave too much excess on the surface, where it can harden and provide a slightly chalky finish, (which will only need removing to expose the wood again, anyway). You need to find a balance where you leave enough to fully fill the open pores – but not too much to make removal of any excess, difficult. For that reason, it’s best to work the filler into the wood with the grain, and then to remove most of the excess by scraping the finish after it’s been left to evaporate and thicken for an hour or so. This scraping is done across the grain – so as not to pull the hardened finish out of the pores again. Once the filler has thickened for an hour or so – it’s much more like a putty, and it’s easy to see where you need to scrape to work back towards the surface of the wood. All surfaces are filled, and care is taken when scraping back to leave the exposed grain filled as much as possible. Any open holes and routs are cleaned and scraped out also. You don’t want to let the filler harden and close up any of the through-body string holes, or around the edges of the string ferrules.

20190325_104651

As with all fine finishing – it really helps to work into the light to check the quality of the finish, and it’s always good to revisit any problem areas which have previously been identified – to make sure the filler is doing it’s job.

20190325_104705

With the body grain filled and scraped down, the body blank is hung up to dry for a day, to allow the filler to fully dry and cure. Once the carrier has cured, the filler should be bonded into place, and the fine surface finish can then be re-established by working over the body with 320 grit. Again – working with the grain to disguise any sanding marks as much as possible.

20190326_094810

The idea is to sand the body back to the wood – through any of the filler coat, which may have accumulated on the surface. It’s important however not to sand too hard, and end up removing the grain filler from the pores, and fine detail. I like to re-establish the edges of the body by gently rubbing down with a little grit paper and my fingers – before a general rub over with grit paper over a backing block on the flat surfaces. By working over the whole body, methodically, it’s possible to restore the original level of finish – but this time with the grain filler in place to smooth out all of the grain imperfections.

20190326_101541

Then, after a good clean over with a tack cloth, the surface of the wood can be sealed. I’ve used a sprayable sanding sealer before – but this time, I have a bottle of Mylands Lacacote Sanding Sealer kicking around from a previous framing job.  The weather is still a bit too cold to easily spray shellac and lacquer and, besides, I want to try and pay particular attention to the finish on this project. This sealer usually gives really good results. I’ll apply the shellac by hand.

20190326_110815

The sanding sealer is, in effect, a much more liquid version of the grain filler, and is also designed to seal the surface of the wood down to a very fine, sandable level. Being shellac based – the carrier is, again, spirit based – this time thinning with Methylated Spirits. A coat is applied over the entire body with a rubber, or a suitable mop brush, and then left to cure for 24 hours before being keyed back and flattened with 400 grit paper. All in all – three coats are built up – flattening back in between, to provide a consistent matte finish where, importantly, the wood is fully sealed. It’s important to try and keep the sealer coat as consistent as possible – since the flatting back is intend to be a light rub over, only. You really don’t want to have to rub out drips, sags and runs at this stage if you can help it. Shellac can really clog your grit paper, (although Sanding Sealer is intended to provide a surface which is a little easier to sand, and therefore less likely to clog).

As the surface is flatted back, and lightly re-keyed for the next coat – it helps to work into the light to make sure any shiny areas are dulled back. Small patches which stay shiny show up areas which are slightly lower than the surrounding – so by working over the body, checking for such areas and then flat-sanding them out – all the surface imperfections in the wood are gradually filled. The result is a super silky, absolutely flat piece of lumber, with a sealed matte finish. If you do find sags or drips at this stage, it might be necessary to sand them back level, and then apply spot coats of lacquer to help keep the overall coat consistent. In really bad cases – if you miss something – you may have to let the sealer completely cure before it’s safe to sand it back level, and then recoat.

20190326_111915

Also at this stage, I like to seal inside the cut outs and body cavity routs as well, with at least one of the coats of sealer – but I always try to ensure that the neck pocket stays totally clear of any sealer at all times. This will help provide the best wood-to-wood contact between body and neck. It’s not usually necessary to finish inside the cutouts to such a high level as the rest of the body – but by applying some finish there – at least the protective characteristics of the finish can extend all over the entire body.

It should now be possible to apply the painted design, without the risk of the paint carrier being absorbed into the wood too much. I’m finishing a test piece of ash in parallel with the project – to double check the compatibility of various finishes. At this stage, I still have high hopes for a casein painted design. Before that, however, I want to make sure the sealed finish cures, and that it tones the wood the colour I need to approximate Pages’s original guitar. It may well be that I’ll have to tint the finish a little over the sealed wood – ash can sometimes be a little pink, rather than the yellow / gold tones seen on many of the library images I’ve found. If so, that will most likely have to be with a few spray coats of light amber tinted nitrocellulose . Having used shellac to seal the wood – any nitro coats over the top should be fully compatible. What is more, I should then be able to flat back any tinted coat, enough to act as a neutral base for the painted design. The plan is then to use a protective clear nitro coat to finish the entire body – perhaps flatting it back a little from a full gloss, before a final finish and buff with Renaissance paste wax. That’s the plan at the moment anyway. I’ll leave the three coats of sealer to harden, cure and shrink back for a week – and then take a look at the tone and colour of the body to see where I need to go from there.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s