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Steve Getsiv

Ground Coat - Testing a Modern Finish

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I've been lurking on this site for the past few months as I have done a complete rebuild on my cello - which I purchased on craigslist for $250 last Summer. I'm an engineer by education and have been taking things apart and putting them back together my whole life. 

After doing an initial set up, I wasn't happy with the sound, especially of the D string. I started with carving a new bridge, and have since carved 4 more, always trying to improve my skills. I tried different sound post positions taking notes about how it affected the sound. I then researched fingerboard undercutting and tap toning of the fingerboard itself - I finally got up enough courage to pull the fingerboard and relieve the back side - originally it was very rough, carved by a team of beavers, most likely.

The instrument got better and better as I did this work but still wasn't even as good as some of the shop German cellos I played in local Portland shops. It became obvious to me that the plates were way too thick so I took a deep dive at platetuning.org and read every article I could find. After taking the instrument apart twice, I eventually came to realize that "free plate tuning" is not the final answer but fixed plate tuning (I ended up building a jig for the belly to hold the edges in place), worked really well and helped my focus on thinning the areas that needed attention. After my second regraduation session, the cello really started to sound great - better than anything I could find in shops up to $20K. 

I replaced the bass bar as well - ended up using a reverse triangle, Christian Bayon style, without the cut outs between the bass bar and the belly. I'm well aware of how resonance / stiffness works - the more weight away from the fulcrum, the lower the resonance frequency, and the stiffer the material at or near the fulcrum, the higher the resonance frequency - so it's therefore possible to both raise or lower the natural frequency of a fingerboard.

Anyway, I digress. Nothing I mentioned above is all that interesting and certainly not unique other than tuning plates with jigs which doesn't seem to get enough recognition. I'm posting today because I decided to remove all that nasty sprayed on finish and recoat the instrument with what I think is likely a unique approach, at least not one that I have read about yet.

Several years ago, in partnership with a Portland, OR based manufacturer of specialty coatings, I designed a wood finish for exterior decking and siding - usable on both hardwoods and softwoods (novausawood.com is my company and the product is ExoShield). We wanted to create something that would outlast all the Linseed Oil / Vegetable Oil based coatings that do not perform well in exterior conditions. We use only Pure Tung Oil from China, in a mix of polymerized and unpolymerized (we add some accelerators to the mix to help the overall finish dry quicker); then we add UV blockers, a fungicide, transparent iron oxides and just enough low VOC solvent to help it penetrate. It's technically a phenolic resin not an alkyd resin. We make this stuff in clear as well as 6 different colors. 

After reading about ground coats and how it can affect the sound of the instrument, I decided to give my Tung oil formula a try. I laid down a couple thin layers of clear on the entire instrument and then laid down a couple thin layers of a 50/50 blend of Mahogany and Walnut with a little added transparent dye from Rockler - I used the TransTint brand. I lightly wet sanded between all coats. The finish dries quickly - within 12 hours in 80-90 degree heat; remember it's made from polymerized Tung oil and has added drying accelerators. 

After working on this refinishing for the past week or so, I finally did initial testing last night. I was absolutely blown away by how much more beautiful my cello sounded. Gorgeous overtones, no harshness, long ring time. I still intend to do a French polish to finish off the instrument so I think it might brighten up a bit more. I started playing around 8:30 pm last night and just couldn't put the instrument down until well after 11 pm. 

 

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Interesting approach. When you removed the original finish, did you go down to bare wood? How did you prevent the oil finish to penetrate too deep into the plates? Generally we want the finish on the  surface rather than in the wood itself, the latter deemed to dull vibration and thus adversely influencing sound.

Anyway welcome to this forum, we all suffer from "violinitis", its incurable! ;)

 

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I started by rubbing with alcohol, tried a little scraping but not successful. Ended up using citrus stripper, then scraping to clean it up perfectly. The finish may penetrate a bit more but it’s Tung oil so remains a bit flexible. 
 

All I can say is that it just sounds fantastic. I played a couple other nice handmade instruments today with the maker for comparison and we both agreed that my instrument had stunning tone, especially the A. 
 

We also agreed that the primary job of the instrument is to motivate the player... it’s a relationship - you should want to spend more time together (with your cello). LOL. 

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On 1/16/2020 at 4:23 PM, Steve Getsiv said:

  Gorgeous overtones, no harshness, long ring time. 

If you can still get all of that when the rainy part of the year shows up in your neck of the woods consider it a success I guess. 

Maybe take note of measurements now like overstand height, string height above fingerboard and projection at the bridge to compare what happens when soupy weather shows up later this year.  Losing some of the effects you're experiencing now can be the norm.  Saturated wood is harder to move with a bow. 

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Hi Steve,

I enjoyed reading your comments on graduating plates using a fixture. I've been wanting to begin bass bar shaping using a similar fixture for a number of years. 

I have a couple questions about the varnish. Is it fair to say your product is similiar in composition to a typical phenolic based spar varnish? You mention it's colored with transparent iron oxides, but there are six colors available. Are the different colors achieved with differing amounts of iron oxide or are different pigments being employed as well? The availability of transparent colors would be the main reason I switch from the current commercial varnishes I like.

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Secretly we all dream of finding that elusive varnish hiding in plain sight somewhere on a hardware shop shelf. It will probably never happen but it won't stop us from trying. Decking oil will penetrate too much and the refractive index is unknown due to the oxides mixed into it. Perhaps its working now but we would need to see some long term data before calling it.

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Back when Craig Tucker was still posting, he was an advocate of a particular brand of hardware-store spar varnish. So I tried some, and with some dinking around, was able to get it looking very much like "my" varnish, at least initially. No, I wouldn't expect the two to have the same wear properties.

I had a similar experience with Violins88's iron oxide nano colorants. Was able to get some impressive results. Again, not exactly like what I do, but darned impressive. My guess is that most people wouldn't be able to tell the difference.

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Welcome to the forum, Steve, and congratulations on your results.  :)

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On 1/18/2020 at 10:29 AM, Joey Naeger said:

I have a couple questions about the varnish. Is it fair to say your product is similiar in composition to a typical phenolic based spar varnish? You mention it's colored with transparent iron oxides, but there are six colors available. Are the different colors achieved with differing amounts of iron oxide or are different pigments being employed as well? The availability of transparent colors would be the main reason I switch from the current commercial varnishes I like.

I think that marine spar varnishes are very different - they go on very thick and are a film forming finish - they are not designed to be flexible and will basically just sit on top of the wood. They are alkyd based from what I have found on line and they are polyurethanes such as Man O' War, Varathane and Rustoleum. The Epifanes brand claims to be made partially from Tung oil but I don't know if it's polymerized; they just don't say. In any case, since I know exactly what is in my finish and there are no marketing gimmicks. The formulas for the different colors are exactly the same other than the amount and colors of the transparent iron oxide pigments. 

Just to be clear, I put down a layer of clear first and then put down my color layers in very light coats. I wanted to put down the clear first to seal off the natural differences in grain color, not allowing the color to darken the lower density spring wood which would absorb more of the color than the late / summer wood.

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3 hours ago, Joey Naeger said:

Thanks for your reply Steve. So just to make sure I understand, you feel your finish has low build per coat and is soft and flexible once cured?

Low build most definitely. Soft? No. Flexible? Only slightly. 

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