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  • GluBoost GluDry, Fill n' Finish, and MasterGlu Instrument Finish Repair

    By Chris Loeffler |

    GluBoost GluDry, Fit n' Finish, and MasterGlu Instrument Finish Repair

    Can this stuff really repair a damaged guitar finish?


    by Chris Loeffler


    Instrument repairs, like vehicles, are typically something I leave to professionals. The chance of a shoddy job or even doing more damage far outweighs my confidence in my untested repair skills! As a result, anything short of a major issue tends to go unaddressed on my instruments. With that as a background, I agreed to check out the GluBoost line of finish repairs and wood adhesives. I was sent the following products to review: GluDry, Fill n’ Finish Pore Filler, Fill n’ Finish Thin, MasterGlu Thin, and MasterGlu Ultra Thin.


    The Fill n’ Finish formulas (Regular and Thin) come in 2 oz. bottles and are intended to address dings, cracks, and dents in any wooden instrument finish, including Nitro, Lacquer, Poly, and even water-based formulas. GluBoost engineers recommend using the standard Fill  n’ Finish formula on porous woods, such as rosewood or mahogany and the Fill n’ Finish Thin for less porous woods, such as maple or Koa for appropriate penetration.


    I used the Thin n’ Finish to address a pretty dramatic gouge  in the back of the neck of an Epiphone Les Paul and smaller ding on the side of a Breedlove acoustic guitar. Armed with no previous finish repair experience and a few instructional videos from the GluBoost site, I was able to quickly and cleanly fill both areas. The adhesive pours fairly viscous from the bottle and sets very quickly. I found the flow very easy to control and was impressed that it kept its height and didn’t dimple in as it dried. The end result was a transparent, bubble-free, smooth finish with no transition lines. Evidence of the original damage was still visible on close inspection from certain angles, but that spoke more to my need to have better prepped the area before application.


    GluDry is a non-blush drying accelerator for cyanoacrylate finishes (such as the formula used in the Thin n’ Finish), and is sold in a 4 oz. spray can. The goal of accelerating the drying process is not only to reduce repair time but also to provide a quick set to reduce the chance of dust adhering to the drying finish or accidental impressions on the surface due to premature physical contact.


    To see how big a difference GluDry made to the process, I only used it on one of the dents I addressed with Thin n’ Finish. My initial concerns that the GluDry might displace the setting finish or cause spotting were entirely unfounded, as the adhesive nearly immediately hardened, transparent and smooth. I also had none of the frosting I experienced in my uncured attempt that I needed to buff and polish out.


    MasterGlu is the wood adhesive formula meant to address repairs such as setting inlays, bindings, refretting, and other true and permanent repairs to an instrument. MasterGlu is sold in 2 oz. bottles and comes in two formulations, MasterGlu Thin and MasterGlu Ultra-Thin with varying levels of viscosity.


    MasterGlu Thin, the thicker of the two, was noticeably thinner and easier to apply than generic purpose cyanoacrylates like Krazy Glue, and had a way of seeping into the right area without needing too much manipulation. I used it to tighten up a couple of loose appointments on an old beater acoustic, securing the pick guard and securing a loose jack. The glue dried transparent and smooth and didn’t swell out beyond the application area as it dried. MasterGluUltra-Thin was noticeably less viscous and worked well in invisibly securing loose binding on the aforementioned acoustic.





    GluBoost turned out to be an easy, affordable solution to the problem of minor instrument repairs that I had avoided addressing the last couple of decades. A semi-steady hand and some time with their instructional videos resulted in like-new repairs and a more playable instrument. Finding out, after the fact, that GluBoost is used by companies like Reverend Guitars gave even more credibility to the long-term effectiveness of their formulas. -HC-





    GluBoost Website



    rszchrisphoto-21e10e14.jpg.62d9f28e525b81107b92a88a3647aee2.jpgChris Loeffler is a multi-instrumentalist and the Content Strategist of Harmony Central. In addition to his ten years experience as an online guitar merchandiser, marketing strategist, and community director he has worked as an international exporter, website consultant and brand manager. When he’s not working he can be found playing music, geeking out on guitar pedals and amps, and brewing tasty beer. 


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    Thanks for the review, Chris.    I've looked at the Glu-Boost products and discussion at one of the lutherie forums has been positive.    

    Were you happy with the way the drop fills buffed out?   Did you scrape, sand (if so what beginning and ending grits), use Micro Mesh or similar and/or buff (which products and methods?)?     I'm assuming that both the Epi and Breedlove were poly - were you able to blend the drop fill into the finish to your satisfaction?

    Even tho the manufacturer says its OK for nitro, there was a comment on one of the forums that it did soften or react with nitro - was your beater by any chance finished in lacquer and did you have any issues?    Again, when you did your repairs on the beater were you happy with the scraping/sanding/buffing?   How did you apply glue to the cracks - straight from the bottle, wick tip, pipette or ??   Last question about cracks - would you be comfortable gluing the crack with one of their products and using another adhesive for cleats (probably AR) - I just can't imagine trying to position and clamp a cleat covered with CA

    I'm also interested in the accelerator - the ones that I have used did cause some whiteness and the CA sort of blistered up, making it slightly more difficult to scrape, plus they get really hot when they kick off.   It sounds like you had no problems with the accelerator (also assuming that you sprayed it on top of the CA, not applying to the surface first which is sometimes done).   Did you wear breathing protection with either the glues or the accelerator (I have become very sensitized to cynoacrylate and have to wear a respirator whenever I use them).

    Their tint kits are pretty interesting - I have used tinted CA (amber and black) but matching color on existing guitars has always been a problem.   The kits are pretty expensive but I'll probably have to pick both the traditional and bright colors.   

    Getting repairs to look good is always difficult - I tell my customers that it will be structurally sound but might not look as good as I would like.    I'm always looking for better ways to do cracks and dings, particularly on poly.    Might have to give these a try.

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    Chris, I'm going to add one more question to my previous comment.   Since you can buy cynoacrylate glues from a number of sources, including lutherie supply houses, model and hobby shops and hardware stores, what is the advantage of Glu-Boost over any of these other products?     I use a fair amount of very thin CA for repairs and installation of binding and purfling - why would I want to consider this product?

    According to the link in your article, 2 oz of the ultra thin Glu-Boost sells for $15.00.   LMII sells it for $20.75 (interesting mark up, eh?).   They also sell another thin CA called Hot Stuff for $11.03, half the price of the Glu-Boost.   StewMac sells their own thin CA for $5.73 for 1 oz, roughly the same as the Hot Stuff, but currently have it marked down to $3.84.    There are similar and significant savings with other CA products.

    I have used both the StewMac products and Hot Stuff and have been very satisfied with both.   I do think the StewMac accelerator leaves some white haze (which is why I asked about it in my previous question).   One significant problem is that usually the bottles clog up long before the glue is used - caps become glued to the bottle and require pliers to remove, the tips get plugged (yes, I know that Glu-Boost has a little pin, I usually use a piece of wire like a guitar string).     I actually think its better to buy smaller quantities of the glue to minimize problems with the bottles.

    The one product that does look attractive from Glu-Boost is the tinting powder and I may end up buying both the vintage and modern kits (at $44 bucks each they are pretty darn expensive too).    I do have StewMac's amber and black medium CA and they work fine for drop filling those colors but from time to time I'm asked to repair a colored guitar.

    Anyway, I would be interested in  your thoughts why these products might be better for lutherie than some of the other things on the market.

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    There are many reasons that GluBoost products are superior to other products.  First they offer far higher performance on all levels. They are manufactured to much higher tolerances, require many more processes to obtain their unique level of performance, and are clearer and therefore result in a better result overall.  Additionally, they are purer, contain no carcinogens, and stored fresh in chillers to maintain shelf life and stability of performance.  in addition to being packaged in a bottle with a grossly superior dispensing mechanism, because they are fresher, they do not harden in the bottle and again, consistently offer a clearly better result.  And when used as directed there are no issues using any of the GluBoost products with Nitro.  Guys do it all day long.  Regarding the MasterTints they are very concentrated and offer huge value.  Also, MasterTints are specifically designed to work with Gluboost products.  One can mix and match any color and with flexible Fill n Finish or the Ultra High Performance MasterGlu CA products,  the results are grossly superior and offer huge value over other cheaper products i believe that is the reason that all the top techs and builders are using it.   

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