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Nick Allen

Is this ground acceptable?

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One part clear dewaxed shellac, and four parts denatured alcohol, a la Michael Darnton's recipe he mentioned in one of his varnishing papers.

Am I doing anything wrong here?

IMG_20170428_182841.thumb.jpg.302b0a7c75a1dbd68bd7e612ce39e1b7.jpg

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I know the sand sealer is supposed to be dewaxed, but I think the sediment is wax.  I would decanter into another jar leaving the sediment behind.  I use this stuff for clear dewaxed applications (furniture).  

https://www.amazon.com/Dewaxed-Platina-Shellac-Flakes-Lb/dp/B012AEO32E/ref=sr_1_1_a_it?ie=UTF8&qid=1493434856&sr=8-1&keywords=platina+shellac  

Dissolves quickly in 190 proof everclear with no sediment.  

-Jim

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with this approach you can use either wax or dewaxed.  It is personal preference.  Experiment both ways if you want to see if you notice a visual or acoustic difference.  My guess is you will notice little or no acoustic and maybe a subtle visual.  Just make sure the shellac is fresh enough to dry properly.  Good results either way.  Never had any issues with putting oil varnish on top of this ground either wax or dewax.  It is fairly fool proof approach with consistent results.  Not a big fan of denatured alcohol, maybe just overly cautious.  You don;t need to be overly concerned with proportions, just make sure shellac is super thin.  I don't use this ground any longer but from what I recall, you could start with higher dilution if you want..  You would just need to put on more coats.

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I haven't been able to find exactly what's in the Zinsser shellac, but the "sediment" could be fumed silica which is often used to cut down on glossiness.

Personally, I wouldn't use shellac as a ground, particularly on maple.  I have consistently found that shellac gives a result similar to an all-over "glue ghost", i.e. lost contrast and grain detail.

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8 hours ago, Nick Allen said:

One part clear dewaxed shellac, and four parts denatured alcohol, a la Michael Darnton's recipe he mentioned in one of his varnishing papers.

Am I doing anything wrong here?

Yes Nick, you're believing Michael Darnton's advice that shellac is a good ground. You're a musicican also, so you understand tone. Shellac will give you a 'toppy' sound. You don't want a screechy violin do you? I believe Stradivari used linseed oil as the ground. That's what I use and it gives a nice sound all round. It just takes a lot longer to dry. That's the real reason why shellac became poplular from the mid 18th century onwards, it dries quickly.

But how many violins will you make per year? Not many, so you have plenty of time to let one dry while you get on with something else. You don't need a fast drying ground or varnish.

Just because lots of other luthiers do it this way, and have done for nearly 300 years doesn't make it a good idea.

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Shellac is not a bad ground but I would suggest using amber rather than clear as it will give a golden yellow color to the ground.   It may not be the best thing optically,  neither is pure linseed oil but either one is adequate.  Shellac will seal better.  

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I find shellac useful when used in a ground but I thin it down and add other resins to it. I normally will use it as a thin sizing coat and very sparingly. I have used Zinnser sanding sealer but now prefer to make up a small fresh batch from de-waxed blonde flake and Everclear. The fresh shellac is then filtered through cheese cloth and a paint filter.

To this I can add other things to adjust the color and elasticity and I only use it in one thin single coat. It works well and refracts nicely. I have used other resins in alcohol the same way instead of shellac. It's important to experiment first on samples because once the wood is sealed it then becomes harder to introduce more color into the wood.

 

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6 hours ago, sospiri said:

Yes Nick, you're believing Michael Darnton's advice that shellac is a good ground. You're a musicican also, so you understand tone. Shellac will give you a 'toppy' sound. You don't want a screechy violin do you? I believe Stradivari used linseed oil as the ground. That's what I use and it gives a nice sound all round. It just takes a lot longer to dry. That's the real reason why shellac became poplular from the mid 18th century onwards, it dries quickly.

But how many violins will you make per year? Not many, so you have plenty of time to let one dry while you get on with something else. You don't need a fast drying ground or varnish.

Just because lots of other luthiers do it this way, and have done for nearly 300 years doesn't make it a good idea.

Controversial....

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Hmmm??  Changing the subject a bit but since I used it on one violin, I thought I'd mention;

I see "oil" and "linseed oil"  mentioned here and other places in violin finishing.

Way back in my memory when I did some other wood working and was looking for a good finish I did much research that is a bit hazy now.  But in comparison to any oil or linseed oil, Tung nut oil (pure, unadulterated) was far superior to any other and used by fine furniture makers and re-finishers.  It gave a far clearer (but slightly colored) finish that was far more hard & durable but less likely to chip or spot from any liquid?  If properly applied it can by a very adhesive surface finish, or soak deeply in.

???

 

 

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All the old Cremonese instruments have been french polished haven't they?   Or am I mistaken in that?   Those applications may contain other resins besides just shellac though.

 

 

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6 hours ago, sospiri said:

Yes Nick, you're believing Michael Darnton's advice that shellac is a good ground.

Just because lots of other luthiers do it this way, and have done for nearly 300 years doesn't make it a good idea.

This guy... lol. I find his remarks troubling sometimes.

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I will have to pay attention to the potential for screechiness of tone since I use a very dilute coat of dewaxed blonde shellac as a sealer.  Once the instrument is well-tanned in the Texas sun, I like the look at this point, but the varnish of course is a factor.  The fiddle is an older one, the workmanship indifferent at best.  But you can get an idea of what the shellac looks like.

20170419_173207_001 crop.jpg

20170419_173146 crop.jpg

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:) It appears there is no film build up on the wood which is how I use a shellac/resin size. Very thin non sealing coat and then start building on top of this.

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2 minutes ago, lpr5184 said:

:) It appears there is no film build up on the wood which is how I use a shellac/resin size. Very thin non sealing coat and then start building on top of this.

Thin enough test for me is whether I can still feel the wood through it.  But again, shellac clearly is not for everyone.  And as noted above, we'll see about the tonal impact -- initially after being set up and then a month or two later (before changing out the post and bridge).

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The first few instruments I made I used thinned shellac for the ground and the sound is good. It's easy to use so that is a plus. The thing I don't like about it is the ghosting effect Don mentioned. I don't antique instruments yet so the only place the ghosting showed up on those instruments was at the transition areas to the neck. That could have been dealt with at the time if I would have over laped some colored varnish on those transition areas. Now days I finish the neck first and over lap the colored varnish. Makes for way better results IMO at least in this transition area. 

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6 hours ago, Eryri said:

Controversial....

Yes, and sospiri never missed a single opportunity, no matter the subject of the thread, to champion this approach. Points for persistence are in order, at the very least. I will reserve judgement until such a time as I have tried it, first on scrap.

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3 hours ago, Julian Cossmann Cooke said:

I will have to pay attention to the potential for screechiness of tone since I use a very dilute coat of dewaxed blonde shellac as a sealer.  Once the instrument is well-tanned in the Texas sun, I like the look at this point, but the varnish of course is a factor.  The fiddle is an older one, the workmanship indifferent at best.  But you can get an idea of what the shellac looks like.

20170419_173207_001 crop.jpg

20170419_173146 crop.jpg

Julian, did you rub or brush the dilute coat on?  I'm currently experimenting with application methods for this kind of seal coat.  The trick is seeing how much color I can get into the spruce without the spruce going splotchy.

-Jim

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4 hours ago, Julian Cossmann Cooke said:

Once the instrument is well-tanned in the Texas sun, I like the look at this point, but the varnish of course is a factor.  The fiddle is an older one, the workmanship indifferent at best.  But you can get an idea of what the shellac looks like.

(images omitted from quote to save space)

Julian, it's not possible to say anything meaningful about those photos until some more coatings go on and we can see how the flames react.

I have been doing a lot of ground/varnish tests this week, and here is an early one testing a wide variety of possible grounds.  I didn't like the shellac, neither did I like a thick paste (another pale one to the left).   From there, I fine-tuned the ones I liked best, currently ending up with the one you see at the top (it's a different piece of wood, much nicer than the dark, unscraped sample in the first test).  I don't have the final varnish on the good test yet; it's just a 2-stage ground:  colored copal in solvent, followed by a short oil varnish thinned out a lot.  Color, intensity, viscosity, penetration, wetting... a lot of variables to play with.  And I would do something different for spruce, where acoustics is more important and aesthetics less so.

590540033ef03_Groundandvarnishtesting.thumb.jpg.30d1975658360da203b4d7589a7bd008.jpg

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One thing to note is torrefied  wood is darker than starting out with white wood. So that can be an advantage when finishing especially on the spruce top. I find sunshine to give the best color if you have the time. I have some torrefied wood and it has a different look than UV exposed wood. UV wood looks more golden. The roasted wood is more brownish and when using torrefied wood I'll add some amber color to compensate. I'll try and post a side by side comparison photo.

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