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sandman

The Purpose of Ground?

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I've been building furniture for around forty years or so. But not until I started dabbling in violin making a couple of years ago did I ever hear the term "ground." I'm now working on my eighth instrument and I confess I'm still a bit in the dark. The books and YouTube videos I watch all say to apply a "ground" of this or that to the bare wood prior to the varnish. So I do. But I have never have found anything to explain what, exactly, it does. I have assumed that it is to seal the wood somehow or make a better bond for the varnish. Am I correct? Is that all? Does it have anything to do with improving the tone of the instrument? I would really appreciate some words of wisdom from someone who knows what they are doing in this area. I prefer to make educated choices in what I apply.

Thanks in advance!

Edited by sandman

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The ground is the base of the varnish layers. Varnish, oil or spirit, has no problem sticking to clean wood. In fact, varnishes love wood too much and soak into it which causes unsightly blotching and even tone problems. Materials used for grounds include shellac, casein, hide glue, egg whites, and various water-based gums. Some makers even mix in chalk and powdered minerals. You can do a search on MN and read what people use. 

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I would disagree with making light and dark grain have less contrast.  I think of contrast in terms of visual appearance.  I like more contrast. but maybe you mean in a more physical sense? 

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5 minutes ago, MikeC said:

I would disagree with making light and dark grain have less contrast.  I think of contrast in terms of visual appearance.  I like more contrast. but maybe you mean in a more physical sense? 

I mean a difference in darkness and lightness so the dark grain would be darker (resulting from absorbing more stain/color) and the light would not change (absorbing less color) because it is less porous than the dark. So, there would be a greater difference in brightness - 

stain.jpg

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This is from Violin Varnish by Koen Padding, it is what I believe is much of the function, to prepare a suitable varnish surface.

001.jpg

002.jpg

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I'm pretty sure that a gesso ground of some sort has a profound effect on the sound. The varnish rubbed in to it seems to stop there, and form a hard shell.

The result is a more focused, clear, articulate sound, with a 'click' between each note.

 

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As far as I can tell, there are several reasons for a ground but only a few good ones. Preservation, sound, appearance and strength are the only good reasons I can come up with. Two of the bad reasons, mystique and marketing may win over the good ones.

Preservation: Putting something like borax on the instrument may help.

Sound: Preventing the pores of the wood from filling could make for a better sound. It is possible that some ingredient such as borax might make the transfer of sound from wood to air, work better. Since the ground is covered, this would be more likely with a distressed finish than a polished one.

Appearance: The classic way to give an illusion of depth to a finish in wood or leather is to first coat with a bright or even somewhat white layer and then cover that with a transparent but darker layer. The materials used in most grounds would seem to support this as a motive.

Strength: There are formulas that are said to strengthen wood. The formulas I have seen thus far don't look like things I would do to a violin. If the formula worked and continue working over time, it would still probably lower the speed of sound by adding mass.

 

 

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"The classic way to give an illusion of depth to a finish in wood or leather is to first coat with a bright or even somewhat white layer and then cover that with a transparent but darker layer."

I don't understand this.  Can you give an example of a coating like that? 

 

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56 minutes ago, Uncle Bob said:

Appearance: The classic way to give an illusion of depth to a finish in wood or leather is to first coat with a bright or even somewhat white layer and then cover that with a transparent but darker layer. The materials used in most grounds would seem to support this as a motive.

 

By "white" I presume you mean colorless. By "darker" do you mean colored?  Or white means lightly tinted and dark means heavily tinted. 

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I have a lot more experience with balsa wood than with spruce and maple.  When working with balsa for (say) a hand launched glider, a finish (usually nitrate dope) is applied which has the effect of hardening the surface and stiffening the balsa.  I assume that the ground can do the same thing with spruce in particular.  My question: do we try to stiffen the spruce with the sealer/ground?  I've seen many cautions not to allow oil to soak deeply into the surface as it has a "rubberizing" effect that would damp vibration.  Do we want the ground to enhance vibration?  In particular for high frequencies which stiffening should enhance?  Thanks

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The Koen Padding excerpt lays most of it out pretty well. I think there is also a structural element as mentioned already. Applying the wrong type of materials could add too much weight, stiffness, or damping. Traditional grounds should avoid this sorts of issues which could have negative tonal implications. The ground also helps give light something to reflect off of from inside the wood. The holographic effect of the flames under a nice varnish is created by having light reflecting back from inside the wood. 

The ground can also help you manage the contrast of the wood. I had an unfortunate mistake, which illustrates this pretty well. I was making a violin, but I only could spend a day or two intermittently working on it (repairs pay the bills). I was initially going to use a red maple back, and had a matching neck and ribs. When I realized the worm damage was going to end up in my finished piece I decided I would table it and go for something that wouldn't need an extra repair, so I grabbed a different set of maple. I forgot to switch out the neck, though. One would think that it would have occurred to me at some point in the process, but it wasn't nearly as obvious before the ground. The Red Maple has a lot more contrast than European, so the ground really accented this difference. What initially appears to be just a color difference is mostly a contrast difference. Without correcting that issue you would have no chance of getting the color to look right because either the dark flame will be too dark or the light flame will be too light.

I apologize in advance if these photos didn't come through properly. For some reason the first 3 show up as links as I upload them, but the 4th shows up as an image in the text box. Don't know why. I uploaded them all the same way.

So, here's the photo of my 'oh $8it' moment when I emailed Joe Robson in a panic.

Ground Issues -2

and here's the same violin after Joe's recommended correction

Ground Issue Corrected -1

After varnishing (a little more color correction happened in the color coats). Not perfect, but I can live with it.

Ground Issue Varnished - 2

20150303-dasler-gh-124.thumb.jpg.06d9b139f7bf3f245024b5ccc341ce6e.jpg

So, the point I'm making is that the ground can give you some ability to make some color/contrast changes that may be harder to accomplish with varnish alone. Not to mention aiding luminosity and creating the 'holographic' effect in addition to previously mentioned attributes of the ground.

Ground Issue Corrected -1

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12 hours ago, MikeC said:

"The classic way to give an illusion of depth to a finish in wood or leather is to first coat with a bright or even somewhat white layer and then cover that with a transparent but darker layer."

I don't understand this.  Can you give an example of a coating like that? 

 

Gladly. One example would be the classic violin finish with a ground. Most grounds are white in tone. After the ground is on the violin is usually a flat dusty sort of white shade and does not look all that great. Before the varnish is added the ground appears opaque and lets very little of the wood's character through. The varnish used is usually quite dark when you look at it in a bottle. After it goes on, it is thinner so it is more transparent than dark. When you add the varnish, a lot of the ground tends to disappear. There is still a light and reflective coating though it is not as evident. The varnish is more refractive than reflective. The effect is that the light comes back from the wood and has a feeling of depth as it is glimpsed through the darker and richer varnish layer.

This method is used by painters. Gesso in the background and a lake on the surface gives a feeling of depth. I first learned this method while studying old methods of treating leather.

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I like to try and look at all these things in historical context, as much as possible.

 

So why was a ground used, trying to answer in terms of presumed historical motives:

1) It's what the makers had been trained to do, and their masters before, extending to instrument making traditions reaching even before the violin

2) It's a variation on what virtually all artisans of the time in Italy did as one of the first steps in coloring or finishing any kind of work.   

3) Ground historically probably literally meant a step of using ground minerals, and not any coloring that came before.

4) General historical reasons for a ground in various arts generally, including instrument making:

  1. provide a uniform undertone to color work
  2. provide a uniform tooth
  3. to provide a bright and generally reflective under layer below any further coloring
  4. add physical toughness

 

 

 

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7 hours ago, Uncle Bob said:

 

This method is used by painters. Gesso in the background and a lake on the surface gives a feeling of depth. I first learned this method while studying old methods of treating leather.

sorry this is kind of off topic but what are the methods of treating leather?    

 

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All this talk of grounds...  let's see some pictures,  I see one,  anyone else ? 

I would post one but wasn't going to bother getting the ingredients until after the build. 

I saw a really nice looking finish on a facebook page but it might not be cool to copy someone else's pic and post it here

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37 minutes ago, MikeC said:

All this talk of grounds...  let's see some pictures,  I see one,  anyone else ? 

I would post one but wasn't going to bother getting the ingredients until after the build. 

I saw a really nice looking finish on a facebook page but it might not be cool to copy someone else's pic and post it here

Here's a fiddle (in a bass) with my ground. It's petty much what Roger described in his bass thread, but i think my varnish, this batch anyway, isn't as dark. The second picture is of the same violin, very lightly antiqued. Sorry if the pictures are poor, just what i have on my phone.

20170603_093441.jpg

20170710_161438.jpg

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To me, when somebody states "ground" I consider this the  mineral portion found on surfaces of the inst. The simplest answer of its presence is the results of surface preparation. Evidence  this is most likely the reason is analyses has shown it is not a complete surface cover, missing in places.   Logic would indicate  it is the residue of sanding/preparation of the surface. A paper on making sandpaper in 1800's (lost title)  said  the grit was collected on the sides of roads made with Belgian stone blocks from the grinding steel of wagon wheels. It mentions it was even graded to some degree in wind rows!  The other likely source of grit would be pumice.  I suspect the mineral content  of each differs considerably and if both were found in areas of easy procurement might indicate merely the result of sanding. 

(David B, anyone who uses the term "tooth" is definitely into the  literature)

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Conor that looks good.   In the antiquing picture is that with a varnish applied?  Does it have anything added to it like lakes for color? 

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On 8/8/2017 at 5:39 AM, MikeC said:

sorry this is kind of off topic but what are the methods of treating leather?    

 

The method I like uses milk paint. The bottom layer is low PH to dissolve the casein. Lime and/or Borax work well for that. The theory is that treated leather is acid and the base will join to it better. (Alchemists thought so at the very least) The top layer is acidic and has oil in it. When the bottom layer is nearly dry, the top layer is added. When casein is combined in and acid and a base layer with oil present, the casein will cross link and make a very tough substance that remains flexible.  This recipe works well on a lot of woods. I think it looks horrid on cedar though.

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