Roger Hargrave Ground with Calcium Sulfate dihydrate Gypsum

[Greg Sigworth]

I wanted to experiment with this ground and possibly use it on the current violin I am making. Being a bit lazy I did not want to spend a week making the Gypsum using Mr. Hargrave's method. There are many sources which sell a powered gypsum, ie. gardening fertilizer, and can any of these work or should I just bite the bullet I do the work described by Mr. Hargrave?  There is a local artist's store which sells an Italian Gesso kit including white powder, I think gypsum, and rabbit glue as the binder. I am going to see what the white powder is made of. I have used a number of times the ground described by Greg Alf in Trade Secrets #1 and I would like to try Hargrave's method. Any advice will be helpful. Thank you.

[charliemaine]

At the time when Roger was sharing this info I started looking into a alternative source for the same reasons. I found that Selenite, Marienglas sold at Kremer Pigments was a good substitute. 

https://shop.kremerpigments.com/us/shop/pigments/11800-selenite-marienglas.html

 

[JacksonMaberry]

I second the selenite/marienglas. Having done both, the results are indistinguishable. Mix it into a paste with a varnish and rub on/off, then cure well. Might have to do this more than once if you want to prevent color varnish entering the wood, depending on the wood. 

Personally I don't find the mineral bearing oil based grounds to be better optically or sonically than an oleoresinous ground used on its own and applied with appropriate consideration, so I don't use the marienglas unless the wood is especially porous. Your milage may vary. 

[Greg Sigworth]

Thank you for the information, charliemaine and JacksonMayberry. I was wondering if Kramer had such a product.

[GerardM]

16 hours ago, JacksonMaberry said:

I second the selenite/marienglas. Having done both, the results are indistinguishable. Mix it into a paste with a varnish and rub on/off, then cure well. Might have to do this more than once if you want to prevent color varnish entering the wood, depending on the wood. 

Personally I don't find the mineral bearing oil based grounds to be better optically or sonically than an oleoresinous ground used on its own and applied with appropriate consideration, so I don't use the marienglas unless the wood is especially porous. Your milage may vary. 

When you say cure well, is that using a uv light cabinet?

[JacksonMaberry]

2 hours ago, GerardM said:

When you say cure well, is that using a uv light cabinet?

UV cabinet, sun, whichever so long as you give it adequate time. That will depend on the strength of your source. 

[Michael Szyper]

You should be careful when applying it with water. This task requires tons of skill in order to make it look right. Combining it with varnish as suggested by Jackson is a bit more wasteful, but very easy to control. 

[Christopher Jacoby]

I think dry gesso is pretty much what that recipe is after...

[Mike_Danielson]

This is not really a gesso because it lacks the glue and linseed oil.  It is a slurry of gypsum that is rubbed in until it almost disappears.  What Harris talks about is a gesso ground.  

The significant thing is Hargrove says the quality of sound greatly improved after doing this--That is why you do something like this--I consider this a significant observation.  The whole point of this is to keep the varnish out of the wood.  

i have come to the conclusion that the observations of Barlow which found particulate matter on the wood surface was on a cello rather than a violin.  This Barlow observation has driven a lot of experiments, technique, and conjecture.   Echard never found it on a violin--that is significant, too.

There nothing saying you have to use particulates to keep the varnish out of the wood.  Organic matter has been found repeatedly on the surface in historic studies.  I assume that is the ground that keeps the varnish out.  I use dilute hide glue for this on violins but a particulate ground on cellos.

[JacksonMaberry]

You can also use varnish, or even oil, to keep varnish out of wood if you understand how to do it. We've seen this in ancient work (Echard and Brandmair) and modern. 

As much as I respect Hargrave, I'm not going to lean into hagiography. When someone, even Roger, says the gypsum ground made the sound (clarification needed) 'substantially better', I'm going to want something to back that up. 

Bottom line to the OP, slap whatever you want to on your instrument after you've thought it over and done plenty of tests. It's your instrument, after all. If the results please you, that's what counts. I've never stopped trying new things, and I doubt I will. I feel that what I'm doing now is great for my optical/sonic aims, but I refuse to believe it's going to make everyone else as happy as it makes me, and that doesn't bother me. This trade and this community gets way to high on dogma for my taste at times, and even a superficial survey of violin history will show that in all stages, there are many, many "correct" methods. 

[John Harte]

21 hours ago, Mike_Danielson said:

i have come to the conclusion that the observations of Barlow which found particulate matter on the wood surface was on a cello rather than a violin.  This Barlow observation has driven a lot of experiments, technique, and conjecture.   Echard never found it on a violin--that is significant, too.

There nothing saying you have to use particulates to keep the varnish out of the wood.  Organic matter has been found repeatedly on the surface in historic studies.  I assume that is the ground that keeps the varnish out.  I use dilute hide glue for this on violins but a particulate ground on cellos.

Mike, it seems that she also claims to have found the same in a violin.  The image below is from this paper:  https://www.academia.edu/89024968/Chemical_and_microstructural_studies_of_violins

[Mike_Danielson]

John, I believe I have seen this picture before.  In going over her data carefully, I came to the conclusion that the provenance of her sample was never clearly established.  Since the mineral ground has not been seen on violins but on cellos, I came to the conclusion that the sample came from a cello. 

In other words,the sample was misidentified when given to her--it is not her fault.   If my surmise is correct, this answers the problem of particle ground on "violins."  That is, it was a cello.  The careful work of Echard and others cannot be dismissed--the only way to explain it is if Barlow's sample was from a cello.

 

[John Harte]

On 2/2/2023 at 5:38 PM, Mike_Danielson said:

John, I believe I have seen this picture before.  In going over her data carefully, I came to the conclusion that the provenance of her sample was never clearly established.  Since the mineral ground has not been seen on violins but on cellos, I came to the conclusion that the sample came from a cello. 

In other words,the sample was misidentified when given to her--it is not her fault.   If my surmise is correct, this answers the problem of particle ground on "violins."  That is, it was a cello.  The careful work of Echard and others cannot be dismissed--the only way to explain it is if Barlow's sample was from a cello.

Mike, I would be surprised if this is not from a violin.  In other places it has been specifically referred to as a sample from a 1728 Strad violin.  This SEM image looks different to any published as part of the initial study which appeared in Nature, The Strad and the CAS Journal.  One of the Strad samples in the initial study came from a 1711 cello rib.  I don't recall mention having been made of the origin of the second Strad sample other than it being referred to as probable.

Barlow and Woodhouse, Echard, and Brandmair are probably not quite as far apart as might be imagined.  The actual data doesn't seem to conflict, just the interpretations.  This has been discussed at length on Maestronet in the past.

[Shunyata]

I have noticed in my own construction (several instruments with and without mineral ground) that a mineral ground makes a difference in tone.

But I also found that being careful not to soak the wood with the ground varnish makes a huge difference in tone.

I wonder if they are related, that mineral ground inhibits wood absorption of the ground varnish.

[Urban Luthier]

When Roger was working on the bass and documenting the PoP workflow i did ask what the resulting chemical composition is of the PoP with the Heat removed. I don't think we ever got a definitive answer. 

I'll ask Roger next time i speak with him, but I doubt he has the answer. Like others I use other fillers as well - in my case pumice.

By the way the varnish analysis in the S&G book notes the use of a filler

[JacksonMaberry]

5 hours ago, Shunyata said:

But I also found that being careful not to soak the wood with the ground varnish makes a huge difference in tone.

This is a substantially important thing - not allowing penetration beyond a few microns. Fortunately there are many ways to accomplish this, and as long as one employs one or any of them, this "soaked" state can be avoided. 

[Mike_Danielson]

On 1/30/2023 at 8:32 AM, Greg Sigworth said:

I wanted to experiment with this ground and possibly use it on the current violin I am making. Being a bit lazy I did not want to spend a week making the Gypsum using Mr. Hargrave's method. There are many sources which sell a powered gypsum, ie. gardening fertilizer, and can any of these work or should I just bite the bullet I do the work described by Mr. Hargrave?  There is a local artist's store which sells an Italian Gesso kit including white powder, I think gypsum, and rabbit glue as the binder. I am going to see what the white powder is made of. I have used a number of times the ground described by Greg Alf in Trade Secrets #1 and I would like to try Hargrave's method. Any advice will be helpful. Thank you.

Greg, I do not think anyone answered your question.  The easy way to make this fully hydrated Plaster of Paris is to use a chemical laboratory stirrer.  The important point is to keep the slurry in motion so it will not cake up.  This stirrer works 24/7 and in a few days will complete the process, all without you having to slave over the container with manual stirring as Hargrave suggests.

I would go on ebay and get one.  The ones I have used have a magnetic stir bar.

[David Burgess]

I might just use my wife's Kitchenaid mixer instead. Don't tell her, OK?

[ctanzio]

Fully hydrated Plaster of Paris is gypsum, or calcium sulfate dihydrate: (CaSO4).2(H2O).

You can slather it on as a paste, or just use a solution and let it crystalize out as the water evaporates. It is somewhat soluble in water so the solution would require repeated applications to get a decent seal to the wood pores.

I've used both methods and prefer dabbing multiple applications of the solution. Less mess and it seemed to give a clearer finish when varnished, but that might be related to how well excess gypsum is removed when using the paste slathering method.

 

[SCorrea]

I'm a new guy here so forgive the  question if it has been beaten to death.  It appears that the ground coat success is somewhat dependant on the speed of the carriers evaporation rate to prevent the mixtures penetration into the wood.  If this is the case, are some really quickly evaporating aerospace solvents worth a look?   Xylene, MEK and Toluene evaporates nearly instantly without residue and I would think using it or a similar "fast" carrier would allow the ground coat to sit on top of the wood with good repeatability and far less risk of wood penetration  than an aqueous carrier method.  There is the PPE requirement, but they are pretty straightforward

Edited February 5 by SCorrea
I spell really poorly at times thanks....

[ctanzio]

I've seen some refinishers use MEK (methyl ethyl ketone) as the solvent for French Polishing (shellac dissolved in solvent). You can see the solvent evaporate rapidly. 

The main problem with the solvents you listed is that they are nasty irritants, affecting skin, eyes nose and lungs. At least one of them has a destructive effect on the nervous system. 

There is considerable discussion on this forum about various grounds and methods of application to prevent significant penetration into the wood. A search should uncover enough information to take up a long afternoon to digest.

 

[Michael Richwine]

On 1/31/2023 at 7:55 PM, JacksonMaberry said:

You can also use varnish, or even oil, to keep varnish out of wood if you understand how to do it. We've seen this in ancient work (Echard and Brandmair) and modern. 

As much as I respect Hargrave, I'm not going to lean into hagiography. When someone, even Roger, says the gypsum ground made the sound (clarification needed) 'substantially better', I'm going to want something to back that up. 

Bottom line to the OP, slap whatever you want to on your instrument after you've thought it over and done plenty of tests. It's your instrument, after all. If the results please you, that's what counts. I've never stopped trying new things, and I doubt I will. I feel that what I'm doing now is great for my optical/sonic aims, but I refuse to believe it's going to make everyone else as happy as it makes me, and that doesn't bother me. This trade and this community gets way to high on dogma for my taste at times, and even a superficial survey of violin history will show that in all stages, there are many, many "correct" methods. 

I watched six years of development tests as my employer tried dozens of mineral ground formulations on otherwise identical violin pairs. I was extremely skeptical at the start, but became convinced, since the differences were consistent and undeniable as I watched the comparison tests. Some formulations made no difference, some were undesirable, some were notable indeed. The differences were undeniable even to a tin-eared uneducated oaf like me. The hard part for me would have been choosing which formulation to use, and of course, this would be moot if he hadn't been making good violins to begin with!  Just one unbiased eyewitness account with nothing to gain. My employer was open and free with any information I wanted regarding making, but other than acknowledging that he uses a mineral ground, the exact formula is regarded as a trade secret.

[David Burgess]

On 1/31/2023 at 8:55 PM, JacksonMaberry said:

You can also use varnish, or even oil, to keep varnish out of wood if you understand how to do it. We've seen this in ancient work (Echard and Brandmair) and modern. 

As much as I respect Hargrave, I'm not going to lean into hagiography. When someone, even Roger, says the gypsum ground made the sound (clarification needed) 'substantially better', I'm going to want something to back that up. 

I do consider Michael Richwine's experiences to be a very valuable resource.