Monday, 14 May 2012

Grain Fill with Acrylic paint and Superglue (CY Glue)

The guitar build nearing the point where I need to think about the finish of the guitar, and having used Sepele, Black Walnut and Oak I felt it would be a shame not to use a transparent lacquer. However a test spray quickly showed how open grained all three are. The largest grain or pore voids by far are in the oak. I looked at all sorts of grain filler and followed a lot of posts suggesting cyanoacrylate (CY, crazy glue or superglue) which looked promising.

However in attempt to speed this up I decided to use a gold metallic acrylic paint to fill the large gaps and then CY glue to then grin fill the rest. I added about 30% volume of water to the acrylic paint and then rubbed it into the surface removing as much excess from the surface as possible. I then rubbed it down with 400 grit  and then sealed with superglue and left it to set. After initial sanding the finish is better than I expected. The gold has filled the largest voids and is _just_ visible when at the right angle. The end grain took more paint but here is an image of the top. I am very happy with this grain fill, the gold goes really well with the oak.

 I will add that I masked the black walnut and Sapele off so they just had the superglue grain fill. The superglue took three wipes and sanding to fill all the grain, but it's easy to work so it's just time spent more than anything else.

Below, poor picture but you can just make out threads of metalic gold acrylic grain fill in the oak. It looks slightly proud of the surface, but isn't.


  1. Cynoacrylic glue for filling the open grain?
    I dunno? I like the gold filled grain idea but not so sure of the super glue. Isnt there plenty of commercial products avail?
    First isnt the glue a bit expensive in quanties to seal your entire surface area? Second, isnt it difficult to get consistient coverage? Is it not too difficult sand? Also the dust is toxic to the lungs... Also some of the sanding sealers will still allow stains to penatrate and will even help achieve uniform stain .... How well will your final clearcoat laydown over a glue base?
    Encapsulating wood in cynoacrylic might not allow wood to freely breathe or expand and contract well and also dont think that it helps with the natural resonance of the wood either. I dont know Roos.... Mainly i would hate sanding it and trying to get it smooth and uniform. Anywhere adjacent to naked wood is going to sand away faster than surrounding ca glue.

  2. Hi,

    I can't tell you how pleased I was with the metallic gold paint. It took a bit of sanding to get the surface back but it worked better than I had hoped. As for the CA, I do realise that I may be doing a follow up later this year reporting the issues of spraying a poly-lacquer finish over a CA base, but the CA was very quick to work, and sanded easily. I got a 20ml bottle for 2 UKP and used half of it. I used the water-thick glue as it covers easily and they put in other chemicals to make the gel type. The trick is to work next to a fan, as the fumes can be nasty, though I am unaware of any real toxic effects. It's sanded back to the wood so there isn't really a coating to encapsulate or quash resonance. It's hard to see where the CA is now as when sanding to 2000 grit the bare wood becomes polished. I think the outcome will be known 6 month from now, but yep, I share some of your apprehension.

  3. Wow... Polished the bare wood down to 2000! You are very patient, determined, and meticulous! Of course you are indeed working on a labour of love. Handcrafted by your own skilled hand! Sounds like the CynoAcrylic worked out really decently for you. Dan Erlewin loves that stuff!
    I doubt you would encounter any finish compatibility problems at this point. Obviously the wood isn't encapulated in it.
    I wonder if you could just teak oil or linseed oil the finish of the natural wood and not bother with a clearcoat? I personally dont care for thick shiny polyurathane on my instruments. Do you know what might be real cool? You might look into a old school hand rubbed shellac varnish finish..... The kind that the luthiers used to traditionally do on classic stringed instruments like those Strativarius Violins. They take this natural powdered shallac flakes and some ethanol and make a waxy paste that they rubbed into the surface. That might look real nice with the gold hues under the surface too!
    Uh-oh! Here I go hijacking your project! (LoL)!
    Well congratulations on your project so far, it seems to be going very well and your ingenuity lends itself well to your accomplishments.
    I admire your resourcefulness in using your desktop graphics app to design and output a template. (i used to work in lithographics in the print industry and have a special appreciation for graphical based design solutions)
    I must tell you how much I have enjoyed following your projects , viewing your thoughts, insights and given opprotunity to share in those observations. I hope that you will continue to afford the time and effort in publishing your accomplishments and experiences with myself and anyone else who have taken notice in your pursuits.
    It seems like we share many interests and are of similar personalities. If you ever make your way to North America please look me up here in Southern California, so I can buy ya a pint or take you out for a cup of tea or whatever you may fancy to partake of......

    1. I have to confess as to why I go to 2000. I was given 30 sheets of the stuff as they were otherwise going in the bin at work. They have a solid plastic backing but cut really well. I have normal wet-dry at 300, 400, 800 and 1200. For me the polyurethane varnish has two advantages. Firstly It goes on pretty much flat enough to start with a wet 800. Other lacquers I have tried in the past seem to orange peel heavily as I always spray too much It ends up with a lot of sanding followed by the invariable sand through on edges and back to re-spray. The second thing I find is its very hard, so it works slowly and I don’t go through once the last of the pits has disappeared. I think the trick with poly is to only put on a few coats after all its robust stuff. I see threads where people spray 15 coats to get the PRS glass look but umpteen coats is a thin lacquer technique and here I agree, it’s too thick. I did look hard at Tru-Oil and also Teak Oil as I had just done the kitchen worktop with this. It’s very easy to apply and will polish, but in the end I decided on a few coats of ploy. Glad to hear you enjoy the diatribe.