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violins88

gypsum pore filler

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Those are some good pictures.  Is that an old Cremona fiddle?  who made it?

Hi Mike, no its not Italian but Dutch by Gijsbert Verbeeck, i suspect he had seen some Cremonese fiddles though or his teachers may have had  at least some contact with Cremona/ Venice, information on these makers are very sketchy.

I think it would help alot to figure out what the Cremonese and other did if they were compared alongside other makers from other areas from the same periods. Amsterdam did an awful lot of trade with Venice and surrounding areas .

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Photography suggestion: Increase the depth of field in photos by using aperture priority, Av, and setting the aperture (f/)  to 22 or as high as you can. The camera will adjust the shutter speed. This will put near and far objects in better focus.  ;)

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:) The lens im using a Nikon 60mm f/2.8D has such a low depth of field at close distance that i dont seem to get around the blur in the edges of the photos. I can back off with the camera but doesnt that defeat the obje ct of macro photography??

Im a bit of an idiot when it comes to photography!

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Now if Cremonese instrument show  this red in the pores then how can the pores be filled with gypsum ,as the red wouldn`t have anyway to get into the pores unless it was sealed with red pigments  If the red is `varnish` and so what is the red ,a dye or colour from cooking varnish?

 

 

Who say it was allways done in one single way?

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I am interested in what type of lighting is being used in some of these sample photos ,there seems to be a strong emphasis on bringing out the red . Cremonese violins ive seen dont often look like that in normal non direct daylight/ room light.  Im not talking about coloured varnish layers here just where most appears to be worn away but still displays alot of colour.

 

I can answer for the couple of photos that I have posted.

The Strad 1696 shot is a close up, probably taken under incident bench light.   (I can't remember....)

The Strad 1721 shot is much more recent and was taken through a cheap hand held illuminated 15x magnifier with the camera lens placed directly on top of the magnifier.

 

This type of lighting does tend to bring out the red in these varnishes.  The colours of these varnishes seem to be a moveable feast with colour temperature/light source often having a huge influence over what is seen.  Having said this, I have taken close ups of several other Strads using the same magnifier where the varnish in the pores is nowhere as near red. 

 

Whatever is in the pores tends to not be overly noticeable when still beneath varnish, unlike the effect that most coloured fillers seem to produce.  My shots are "magnified".  Under normal viewing conditions this sort of detail is easily missed.  The shots were also taken in areas of wear where the pore material was exposed but hadn't broken down into that more obvious dark material.

 

Joe, that's a nice shot of the Guadagnini!

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John Masters made the suggestion that alcohol in usage with the gypsum was a good idea. Yes, I now see why. When I take my wet gypsum and spoon it on a stack of paper towels, some of the water comes out. But inside, much water is retained. Too much. So that when I apply it, it does not want to go into the wood.

 

The alcohol-water mix seems to solve that issue.

 

Thanks John

You are welcome.  But please notice,  I did not use gypsum which is a hydrated calcium sulfate.  I used Plaster of Paris.  The alcohol retards the hardening indefinitely until the liquids evaporate.  I spray it and have plenty of time to rinse out the gun.

 

As to the pore issue,  perhaps a tubual is filled (with some level of hydrated CaSO4)  two or three times its diameter,  maybe less.  A colored varnish will be drawn in by capillary action and then STOP.  That is plenty good to both seal and make an intense color in the pore.

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Wm. Johnston posted a recipe on his website a recipe for preparing a color solution by mixing rosin and sugar. Paraphrased here:

 

As per William's website, place 1 tablespoon rosin and 1 tablespoon sugar in a can.

Heat slowly on hotplate (outside). At some point the mix bubbles, foams up and turns black. William says the sugar is no longer sugar and the rosin, no longer rosin, Well, I think that is what he said. Are you here William?

Remove from heat and cool. Add denatured alcohol, or ethyl alcohol.  This solution, applied to maple, gives a bit of color and enhances the figure.  Also should serve as a sealer. Apply the above solution to maple. Perhaps 2 coats.

Next, take 1 teaspoon JO-3 casein, add enough water to cover the casein. Wait 1 hour. Add a little more water. Stir for 1 minute. Add 1/4 tsp. Mrs. Wages pickling lime. Stir for 3  minutes. Perhaps add another 1/4 tsp lime.

Stir. Add 1 tsp slaked plaster. Stir. Apply, by rubbing, to  the maple which has been primed (sealed) with the rosin_sugar sealer. Add dry slaked plaster directly to the wet casein/plaster. Rub more. Burnish into the wood with some sort of burnisher. (your call).

Remove excess. Allow to dry.

 

Rub with 400 grit paper. Apply some gold alcohol based dye stain, Transtint honey amber, available at fine woodworking stores. Or the yellow stain of your choice. At this point, the maple is very smooth and filled. Almost could be used as a final finish. Joe Robson's amber varnish, which, to me, is yellow brown, rubbed on, looks great. But I would want to add some red over this brown. My taste only.

 

So far, my result looks good.

 

More later.

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John Masters made the suggestion that alcohol in usage with the gypsum was a good idea. Yes, I now see why. When I take my wet gypsum and spoon it on a stack of paper towels, some of the water comes out. But inside, much water is retained. Too much. So that when I apply it, it does not want to go into the wood.

 

The alcohol-water mix seems to solve that issue.

 

Thanks John

Thanks for the nod,  John.   The alcohol is a retarder also.  It allows the layer to be rubbed to the wood.  It makes a mess,  so have some newspapers under it.  It also seems to distribute dyes evenly.  I spray it,  and the the retarded nature keeps it fluid for a long time.

 

I am also experimenting to see if less alcohol can be used.  It seems the 1/3 alcohol is enough.  Would you do me a favor and see if 20% ans 25% also remain fluid...I am overrun with other experiments. This would be nice to know for the case of water-soluable dyes.  All dyes are different.  some don't like alcohol at all.  But a 20-25% solution would be likely good for most dyes.

 

By the way,  I am using plaster of paris which is less hydrated than gypsum.  Perhaps later applications of something in water will cause it to set up hard. 

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