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Collapsable moulds


xania

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Do you use them?

We're all using/making one piece moulds.

A guy was out from England observing the class, and he said he always used collapsable moulds.

He says that they're more accurate. I'm just curious, as I've never heard you guys discussing them.

xan

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Do you know if you're going to put the second set of linings in while the ribs are still on the form? Sacconi takes the form out first, but very few people I know do it this way now, since it leaves the shape of one side of the ribs floating without being defined by the form. I always put both sets in before removing the mold.

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I believe that taking the mould out with both sets of linings in is sufficiently easy that I personally don't see the point of the various strategies employed to avoid doing so, given especially that every single such strategy adds complexity to an otherwise exceedingly simple mould design. The simple one-piece mould has got to be as simple and non-complex as it gets.

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Quote:

Do you know if you're going to put the second set of linings in while the ribs are still on the form?


No idea!

I'll try and steer him towards your method if he's thinking of doing the other one.

As you know, I'm on a fairly steep learning curve at the moment.

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In Sacconi's method, one side of the rib is glued to the back first while the mould is still inside of the rib. Therefore the rib form comforms to the mould completely. The rib structure is not free floating at the time during the attaching process, since the mould keeps the rib in proper form. After the rib is glued to the back, it becomes rigid. Then the mould is extracted the second set of linings are inserted.

On the contrary, C&J's method lets the entire rib structure out of the form and "free floats" during the attachment process to the back and the top. It allows margin of differences to the original shape once the rib leaves the mould. But it is an easier construction method. The mould can be extracted with much less effort. But the maker has to do finite position adjustments to make the rib comform to the original shape.

I also think the biggest advantage of Sacconi's procedure is giving perfect perfling to the edge distance all around the violin. You can only achieve similar result with C&J's method if you get your plate size right (in respect to rib) at the first time. Any additional adjustment to the edge work after the plates are attached to the rib would be visible, because the edge to the purfling distance will be reduced. But C&J's method allows more accurate plate graduation near the edge area.

So there are pros and cons to each. Sacconi's method gives better precision and visual results to the mould, but is is harder to work with. C&J's method is easier to work with and provides more accurate edge thickness around purfling. But it is not as precise to the form.

This is my 2 cents to this comparison.

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With Sacconi's procedure one entire side of the instrument's shape, adjacent to the top, is unsupported, by either the mold or linings--it's just a thin, flexible rib--and can change quite a bit across small areas, ironing out characteristic points in the outline. Gluing in a lining to this flapping rib which is not absolutely perfectly matched further distorts the shape. When the linings are glued in while the ribs are still on the mold, instead of the ribs taking the shape of the linings, they tend to telegraph the shape of the mold to the linings, and the whole thing comes out more closely matched.

The shape in small areas is incredibly important, and losing it a big flaw. With both linings in, the overall shape and dimensions are quite flexible, but small stretches are very rigid. This maintains the overall concept of the outline but keeps the exact dimensions flexible. I don't think there's any question at all now that this is the way Stradivari and the other Cremonese makers did it--it accounts for the wide variations in the exact sizes of their violins while the characteristic bumps of each form always seem to be there.

I don't think there's any other explanation for the very lopsided things you find in Cremonese violins, which very obviously could not have been done Sacconi's way.

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... After the rib is glued to the back, it becomes rigid. Then the mould is extracted the second set of linings are inserted.


Exactly. And during this time you have the whole width of the rib hanging out there completely unsupported, and you've got to get the linings on this without distorting the shape of the ribs. Have you read the C&J book where they discuss specifically how to distort the rib outline by how you do the linings, where you can take up a bit of slack in the ribs by making your linings a bit short and so on? Now imagine the subtle problems you'll have getting your linings in without changing the rib outline at all with the entire width of the rib between the edge being lined and the back for support. Rather than promoting good shape, as you insist, I predict it will be much harder to maintain the proper shape of the ribs on the belly side this way.

Quote:

On the contrary, C&J's method lets the entire rib structure out of the form and "free floats" during the attachment process to the back and the top. It allows margin of differences to the original shape once the rib leaves the mould. But it is an easier construction method. The mould can be extracted with much less effort. But the maker has to do finite position adjustments to make the rib comform to the original shape.


Yes but is this really a problem? You state this as if this is obviously a problem, but it's not. Remember, you have all the time in the world to get the ribs and your back and top aligned perfectly. A popular gluing technique even has you clamp it up without any glue and then add the glue later a couple clamps at a time. I did this and it worked great. And clamping it up without glue gives you all the time you could possibly need to get everything lined up the way it should be. Trust me, it's not hard at all.

Your theoretical mind is misleading you into believing there is some loss of precision here in the C&J method, but whatever precision loss there is would be less than the human eye will detect if care is taken, and in the context of a handmade violin will be completely and utterly swamped by other considerations of woodwork.

Quote:

I also think the biggest advantage of Sacconi's procedure is giving perfect perfling to the edge distance all around the violin. You can only achieve similar result with C&J's method if you get your plate size right (in respect to rib) at the first time.


Given that the plate is traced from the actual ribs, why wouldn't someone get their plate size right? You must remember that before someone does their purfling they must finalize the outline, so if they take the time to do a good job they are getting the outline perfect with respect of the ribs, and then spacing their purfling grooves at as uniform a distance from this edge as their skill can achieve. How again is Sacconi's method resulting in a superior purfling distance? I am not seeing any advantage whatsoever.

On the contrary, if you don't purfling and cut your channel until after you've closed the box, then what are you doing on the inside graduations? You won't establish the graduation completely until you do the purfling and channel, so how are you going to make sure you get the graduation you want when by definition you had to shape your inside arching without the benefit of a completed outside arching to allow you to know what you're going to get?

I believe the benefit of being able to control both the inside and outside arching and graduation by doing all that before the plates are glued on to the ribs is something real and substantial, whereas all of the theoretical advantages you point to with Sacconi's method are abstract and unreal, because they assume an imprecision inherent in the C&J method which quite simply doesn't exist in fact.

Quote:

Any additional adjustment to the edge work after the plates are attached to the rib would be visible,


If you've established your outline properly, then if you can do your edgework without changing this outline, I don't see what possible additional adjustment there could be. You have all the time in the world to establish the outline as perfectly as your skill will allow, using the ribs still on the mould as your guide.

Quote:

So there are pros and cons to each. Sacconi's method gives better precision and visual results to the mould, but is is harder to work with.


I'll grant you it's harder to work with, but I will not concede any better precision nor better visual results.

Quote:

C&J's method is easier to work with and provides more accurate edge thickness around purfling. But it is not as precise to the form.


Your saying this doesn't make it true. Using what we're calling here the C&J method (it's much older than them, but that's where you and I learned it, so there you have it) you can be just as precise as you want to be. There's nothing stopping you, and there's no built-in bias against precision as you continue to believe.

Quote:

This is my 2 cents to this comparison.


I'll see your 2 cents and raise you a nickel!

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A one piece mould will work just fine.

I use moulds that are in several sections and even multi-layered. I even handpick pretty nice wood to make them out of and finish them off somewhat. They are only a about 5% more effective than one piece moulds, but that 5% is all it takes for me to decided to exploit a little extra creativity. I really love working with wood and I like figuring things out so rather than do something less creative - even when it's something like this - I'll opt for the more creative approach. Maybe this is the reason some others do it as well.

A person's "reason" for doing anything will usually determine the way they go about doing it. If you want to (or need to) make money at it, then it's probably best not to do anything extra (which this is) that won't directly reflect in the finished product.

I've seen some of the tools Stradivari used and I'm amazed that he was able to find the time to do some of the nice engravings on some of the simplest of toos and still keep up with his schedule making the instruments.

Tim

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I can see that a 3 piece collapsable mould could have an advantage in preserving accurate edge overhang. The builder could install top and back linings, glue the garland to the back, and then remove the mould. The only difficulty would be finishing the blocks and linings which is easier off the mould.

I have been using a stradivari type mould, but purfling before I glue my plates. I believe this is the technique many use. My frustration arrives when, in the glueing of the garland to the plates, the hide glue acts as a temporary lubricant before it grabs. The inaccuracies in my edge overhang are small but easily detected by the informed and critcal.

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Are you spreading the glue all at once and then just going for it, lining it all up in a hurry as you start to install clamps? I'm wondering if you've tried the technique of clamping it all up dry and then gluing it a couple clamps at a time with a thin blade. That's what I did on #1 and it worked great, and I don't believe you would see any sliding of the plates on the ribs due to the glue, because the plates are firmly clamped to the ribs everywhere but where you're actually gluing, and there's not really the slack for it.

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Seth, I've used both methods in glueing. You're right in that glueing small segments is more accurate, but since the whole garland is flexible even clamping to within .2mm or so on the whole circumference of the garland is not that easy. When you add glue your reference lines are obscured and any errors can be multiplied. Yours is the method I use but I've never been 100% happy with my edges.

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I put glue on first, and then go as fast as I can. I start with the corners; first two on one side, getting them perfectly lined up, and the c-bout also, making sure everything there is lined up and looks nice--looks are my first consideration over anything else. Then I go over to the other side, and do the same. Then I'm push the lower bout around until it's fairly even, and put on one clamp somewhere near the middle to hold it, and work my way around spotting a few clamps to get it more evened out, and then fill in the holes with clamps and whatever pushing is necessary. Then the same with the upper bout.

One thing to consider is that the margin in the c-bout doesn't have to be the same as the others--it's not uncommonly a bit larger. I usually find mine is, too, because I like the look when I adjust things that way.

After all that, usually it's pretty good, and the places where it's off are because of the way I cut the corners to get the look I wanted. If necessary, I go around with a gouge or chisel, and a scraper and slightly modify the ribs a bit so they fit the outline. This correction is usually extremely small.

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Seth... Of course I take this as a friendly debate. You and I both work in the same industry where constructive confrontatoinal discussion are considered part of "life"

Now, a few more things:

1. I call it the Sacconi method vs. C&J method not because they are the proper name. It is simply because the people in this forum are familiar with these 2 books. Please allow this political incorrectness to facilated the convinience of our discussion. I am sure Sacconi did not invent his method either. He probably learned from his teacher.

2. At Cremona violin making school, they show you the Sacconi method:

http://www.scuoladiliuteria.com/photostory/storybrd.html

But of course, the student may have other preferences after graduation.

3.

Quote:

I don't think there's any question at all now that this is the way Stradivari and the other Cremonese makers did it--it accounts for the wide variations in the exact sizes of their violins while the characteristic bumps of each form always seem to be there.


Since you also mentioned that:

Quote:

Gluing in a lining to this flapping rib which is not absolutely perfectly matched further distorts the shape.


Couldn't this difference caused by inserting the linings after the Back? The rib is not flapping using Sacconi's method, only 30 mm away, the entire structure is fixed to the back. If fact, I found it very rigid. Seth... you saw my violin just after the mould was extracted. Was my rib flapping?

4. You may adjust the rib form by losening few clamps at a time. By doing so, you are literally "tracing the dots". Very few people can trace the dots perfectly with free hand. The mould acts as a "tool" to provide precision guidence. When you can use it, why not use it? Even if you can get a very close approximation to "tracing the dots", you may have small distortions from the original curves, hence built in unecessary uneven tension in to the rib.

5.

Quote:

Given that the plate is traced from the actual ribs, why wouldn't someone get their plate size right?


sorry... I know it is a cheap shot, but I just could not resist. You traced from the rib to get your plates. But you did not get the plate size right. sorry....

6. Surely that we have no way of proving which method Stradivari used. But we know what Sacconi used. And Sacconi's violin is displayed side by side with Stradivari's 1715 Cremonese, and a Guarneri del Gesu's violin in the Stradivari museum. There are only 6 instruments in the main display room by Stradivari, Guarneri, Amati, and Sacconi. Simply because Sacconi is a modern maker, I don't think he deserves any less repects.

But Seriously.. I have no intention to discredit or promote either method. As a newbie, I think Sacconi's method would enable me to make my violin "look" nicer. I would consider the C&J procedure after I am completely fluent in all the process, when I have absolute confident that I can get everything right the first time.

I think each person should have his/her preference. And this is what gives the personality to the instrument. In my case, I prefer the method from Sacconi, which is also demonstrated at Cremona's violin making school as well as the Stradivari museum. (There is a section of the museum dedicated to the violin making process) And you think otherwise, I do respect that.

Do I need to raise it to a dime?

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"6. Surely that we have no way of proving which method Stradivari used. But we know what Sacconi used. And Sacconi's violin is displayed side by side with Stradivari's 1715 Cremonese, and a Guarneri del Gesu's violin in the Stradivari museum. There are only 6 instruments in the main display room by Stradivari, Guarneri, Amati, and Sacconi. Simply because Sacconi is a modern maker, I don't think he deserves any less repects."

I think he deserves a lot of respect but can't touch the respect Stradivari warrants. I suspect Sacconi would agree with me. However, I notice you avoid the most important comment I made: that the lopsidedness and inconsistent sizes of Cremonese violins certainly absolutely does prove that they did NOT use Sacconi's method. The molds are extant and available, and, very simply, they don't fit the violins that were made with them. Either method obviously works, but IF you want to do it the way Stradivari did it, don't use Sacconi's method.

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I am not sure what lopsided things you are refering to?

For inconsistancy issue, how do you know they are made with the same mould? Many makers have different "versions" of the same mould. Are there several different PG moulds with different dates?

Also Mould is made of wood. Therefore sensitive to humidity. Cremona is next to Po river. The humidity changes every season.

I got a set of Stradivari mould tracings from the museum collection on blue prints. I was specifically told that not to use the trace as the absolute reference to create moulds, because of the actually mould dimension changes from season to season. By how much? I don't know. Maybe you can conduct an experiement on your mould and measure the difference in the dimensional changes during each season.

Could this be the cause in the inconsistency?

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I'm referring to the fact that the instruments almost invariably have one whole side twisted higher than the other--that is, a line between corners is not perpendicular to the centerline. One side of the upper bout will be higher; the corresponding side of the lower bout higher as well, as if the end blocks were held and twisted slightly relative to the centerline. Also, molds change in width, but not relative widths between bouts, and not in length.

Roger Hargrave offered a really sensible description for how all of the pieces of this puzzle could fit, in a Strad magazine article (a really cool article that isn't noticed nearly as much as it should be) a decade or so ago. He suggests that the neck was nailed on, and then the whole ribset twisted to more perfectly center the line of the neck. I can believe that, but might add that I suspect the lack of multiple molds suggests that the production of ribsets was independent of violins--that they were made, removed from the form, and stored for later use. That appears to have been the procedure with necks, so the concept isn't foreign to the shop.

There's no evidence of a large number of molds in the Strad shop, that is, differing multiples for every model, so you can speculate, but you not prove that this would be a factor. I'm trying to stick with scenarios that are consistent with what we do know.

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"I also think the biggest advantage of Sacconi's procedure is giving perfect perfling to the edge distance all around the violin. You can only achieve similar result with C&J's method if you get your plate size right (in respect to rib) at the first time. Any additional adjustment to the edge work after the plates are attached to the rib would be visible, because the edge to the purfling distance will be reduced."

I recall reading that Strad, and perhaps most/all of the old Cremonese makers, cut their purfling channels after the plates were glued on.. is this true? If so, could it be because they may have needed to make adjustments to the edges first (rib to edge distance) because of distortion of the rib garland? Also, if this is true, how/when did they finish graduating the inside of the plates?

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When I remove my garland from the mould I find that there is a very slight contraction or distortion in the C bouts despite careful low moistue rib and lining bending. Not very much but enough to necessitate some slight force to get my corners to lay as planned. Any deviation at the corners forces inaccuracy into the upper or lower bouts. I don't see a cure other than careful work and a lot more experience building violins.

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Cliff, thank you for your earlier post. It has now reminded me why the Englishman said that he found the collapsable moulds more accurate! It was about the overhang issue.

Can anyone describe what these 3 piece collapsable moulds look like? I can't visualise them, and I haven't been able to find a pic on the net.

It's really for curiosity only, as I myself am working with a one piece mould.

Thanks,

xan

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"...I suspect the lack of multiple molds suggests that the production of ribsets was independent of violins--that they were made, removed from the form, and stored for later use..."

I've been wondering about this for a long time, and your thoughts provide great comfort. With reference to the Strad issue a while ago dealing with the "Messiah", one of the illustrations in one of the articles shows the outline of this violin superimposed on the PG mould. The fit is reasonable, but unacceptable as a "finished" product. However, I use the PG mold myself, and once I tried to make a ribset fit inside this drawing of the outline. Well, I could make the ribset fit the outline perfectly with very little effort.

As an aside, I'm getting really close to the point where I might finish the outline and do the purfling AFTER the plates have been glued to the ribsets. I doubt that the graduation implications will be as bad as some say. After all, it didn't seem to bother Stradivari that much.

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