Violin Forum/Message Board

[stringman]

hello, I am looking for a good crack filler. In the past I have used sandarac and most recently soluvar. I am never completely happy with either. Having seen many instruments with well repaired cracks, I am always wondering what was used to fill the crack?

[OyvindT]

I am not an experienced violin maker or restorer, but my understanding is that crack fillers are not used by professionals.

If there is no material missing, the crack is simply glued with hide glue, clamped, and reinforced on the inside with a patch.
If material is missing, it is normaly filled with a carefully fitted piece of spruce or maple with similar grain or flame.

If pieces are missing you would also have to match the varnish.

[stringman]

thanks as you are correct, wood in not replaced, but once the crack is glued, clamped, and cleated, there is more to be done such as filling the crack and touchup. Hopefully there are some professional repair people who understand the question and will be able to respond accordingly.

[woodwiz]

I use half Sandarac and half blonde shellac, as thick as I can brush well. I apply the narrowest possible bead, let it dry thoroughly, scrape it level, sand with 3200 and french polish just the repair. If the existing varnish is extremely thin, I'll build up just a little FP before I sand.

I am not a high end restorer, but I work on fiddles for a living and get really good results. Hardest part for me is getting cracks clean.

[rs]

The answers given are good ones. This is just to thrown in some observations.

If you are the first to repair the crack, it is much easier to make it invisible as compared to following up previous poor repairs to a crack. The latter can really give you a hands full.

Filler is really only suited for the varnish, not the wood.

The two best roots to an invisible repair is tight fit-up of the crack and perfect high-low of the crack. To do this I usually dry-run the fit-up and use the typical crack repair clamps to draw the crack together. I then place little wood wedges on either side of the crack between the bar of the clamp and the plate. This wedge gently pushes the high part into alignment with the low part of the crack. If it is aligned correctly, a straight edge can be laid across the crack and there will be no light on either side. Once this dry-run is done, I disassemble the clamps, glue the joint and simply re-clamp the joint exactly as done on the dry-run.

If the high-low is not perfect, the repair will be sorely visible. Either a shadow will be visible to one side, or if the crack is shaped afterwards, the original varnish will be removed more excessively on the high side of the crack and create a repaired look that will be noticeable from many feet away.

If the crack is not drawn tightly, a gap will occur that will be darker than the wood and this is also unsightly. Therefore, the above two steps are crucial to “invisible” repairs.

After the glue dries, I touch-up any chips around the crack with watercolor. The “filler” is then added to the crack in the varnish. I use thickened spirit varnish. I open a 2 ounce jar of varnish, pour half into another jar and leave the lid off for a few days. The alcohol evaporates until it is thick. I draw a fine line of this thickened varnish across the crack. I want the varnish over the crack to be a little higher than the original. In about three days this is dried enough to then put about two coats of the normal spirit varnish over this and extending about half an inch on either side of the crack. The next day I use a scraper to take the varnish bead down equal to the top. The two coats of varnish just on either side of the crack/varnish bead protect the original varnish underneath from errant scraping. It is VERY important to avoid removal of ANY original varnish if at all possible as this will discolor the area around the crack and the repair will be noticeable from several feet away. I find the scraper cuts more uniformly if I start it moving before it contacts the varnish. If I start from a stopped position, the scraper tends to gouge the varnish.

Micromesh as suggested is good at this point. Generally, if I use rotten stone, the varnish “filler” ends up shinier than the original and I don’t like that shiny line. To combat that problem, I usually use the micromesh until the sheen is about the same as the original and then French polish this whole area.

I generally follow the above as the repair is clean in appearance, and spirit varnish when used on oil can be removed and adjusted at anytime in the future with no damage being done to the original.

Best wishes and hope this helps.
_________________
Randall Shenefelt

[DonLeister]

Stringman,

What is the problem with the sandarac and the Soluvar?

I have some filler recipes, Nebel's and Weishaar's, actually quite a few, but I have little experience with them. I use Deft with good results, not on fine instruments though. I have heard that it hardens over time.

[stringman]

Thanks for all your great suggestions. they are greatly appreciated. The problem that I have with sandarac and soluvar is that they dont seem to hold up well. They look great when it is first done but having seen previously repaired cracks, I often notice that they are visable again. I am always in awe of instruments that I have seen form the old Wurlitzer, Moenning, and Hill shops that have had crack repairs and yet they still look great? I understand that there are many steps beside the filler that constitute a great crack repair but I am always looking for a better way.

[Michael Darnton]

I know that at one point many restorers had switched over to a synthetic that the art restorers use--something with it's own specific solvent so that it could be removed later without touching anything else. I don't know how that has been going in the long run. The name paraloid is floating around in my head, but I can't remember if that's the stuff.

My experience with Deft was that it works really well and doesn't get hard--I know some 25 year old fills that are still doing fine. But it isn't reversible and subsequent retouch varnish won't bond well with it, so if you use it over too broad of an area, the retouch tends to flake off over time.
_________________
new blog at my site! http://darntonviolins.com/blog
my work sites: http://darntonviolins.com and http://darntonhersh.com

[stringman]

Thanks Mr. Darton, Is there any special preperation for Deft that should be done, and I notice that it comes in gloss and matt. Which is prefered? Thanks. V

[Michael Darnton]

I think people use the matte version, but because of the lack of reversibility, let me make it clear that I'm definitely not recommending it. Some sort of reversible retouching varnish would be a better choice.
_________________
new blog at my site! http://darntonviolins.com/blog
my work sites: http://darntonviolins.com and http://darntonhersh.com

[bacon]

Here is a link to the product Michael is referring to, it is now called Acryloid.
http://www.conservationresources.com/Main/S%20CATALOG/default.htm
For properly repaired cracks showing any depth in the glue line (dark line) I was instructed by Joseph Grubaugh to use lycopodium powder with varnish. Lycopodium is a very fine plant spore ,yellow in color, that will fill the most minute imperfection.
Stephen

[stringman]

Thanks Stephen, Is there any specific proportion in regard to the varnish and the lycopodium? and should the varnish be thickened at all? Thanks again V

[bacon]

Lycopodium spore size is between .04-.025 mm. I fill my void of no more than .2mm,hopefully much less, with the lycopodium spores then apply a thin wash of spirit varnish. If the gap is larger I use wood( splinters) .
If you have done ebony dust and cynoacrolate repairs, it is similar.
Stephen