Wood filler for retouching

[Goran74]

Hello! I have used some fillers for retouching in the past but I would like to hear your "recipes" and ideas on that. 

I have used various glues mixed with color, sawdusts mixed with glues, resins etc... 

Strobel recommends a shellac sandarac mix (at Violin maker's notebook). I used it, but without a lot of success. 

My main problem is that the most of the fillers that I used, have different light reflection in contrast to the wood next to them. They are more opaque, matt, blurry or they lack transparency. 

So, my main concerns are:

1. To be reversible 

2. To be esthetically "right"

3. To be something that does not affect the sound quality

I would appreciate your help. Thank you! 

[Jerry Lynn]

If you are looking for a filler for missing wood fibers, scotchlight s22 seems to be the current best option. It can be colored with various alcohol based colors.  It gets mixed with hide or bone glue and applied to the area of missing fibers (with room left for fill varnish and retouching above).  If it is unacceptable, it can be washed out.

If you are looking for fill varnish recipes a combination of manilla copal, sandarac, and light shellac can work well with copal being the dominant resin.  Additions of aluminum hydroxide can allow you to use softer resins, but may decrease clarity.  Using a matting agent allows you to vary the sheen.  With all fill varnish, the window for easy trimming doesn’t last forever.  

[Jeffrey Holmes]

Recent thread...

[nathan slobodkin]

Lycopodium powder mixed with glue can be useful. Also can put in a little glue dust some powder into the crack and then blow off the excess after it dries.

[Violadamore]

I forget who here first recommended it to me, but mixing very fine wood filings with hide glue or varnish (depending on the situation), has worked well for me. 

[Goran74]

Thank you very much for your suggestions. I will try some of those and I hope to achieve better results. 

[Mat Roop]

On 11/14/2021 at 8:01 PM, Violadamore said:

I forget who here first recommended it to me, but mixing very fine wood filings with hide glue or varnish (depending on the situation), has worked well for me. 

Vda... can you elaborate a bit... which type of situation for wood fillings with hide glue and which with varnish?

Thanks!... Mat

[Violadamore]

20 hours ago, Mat Roop said:

Vda... can you elaborate a bit... which type of situation for wood fillings with hide glue and which with varnish?

Thanks!... Mat

Varnish or lacquer where moisture might be a problem, and hide glue where you've got hide glue anyway. 

[Mat Roop]

Thanks, Vda... makes full sense... Mat

[Violadamore]

1 hour ago, Mat Roop said:

Thanks, Vda... makes full sense... Mat

Note that it's important to use filings cut with a file instead of sawdust (which is coarsely granular) or sanding dust (which has abrasive grains in it).  The little file shavings conform better, and interlock with each other.

On things other than violins, where reversibility is not a problem, I prefer clear epoxy, super-glue, or urushiol lacquer as a binder, but on violins, they are barbarisms. 

[Greg Sigworth]

5 hours ago, Violadamore said:

Note that it's important to use filings cut with a file instead of sawdust (which is coarsely granular) or sanding dust (which has abrasive grains in it).  The little file shavings conform better, and interlock with each other.

On things other than violins, where reversibility is not a problem, I prefer clear epoxy, super-glue, or urushiol lacquer as a binder, but on violins, they are barbarisms. 

Thanks for explaining this, I would have thought sawdust was OK. 

[Violadamore]

8 hours ago, Greg Sigworth said:

Thanks for explaining this, I would have thought sawdust was OK. 

Lots of people use it in glue-based fillers, especially for larger divots or voids.  I just didn't find it the best thing for the fine work necessary on violins.

[David Burgess]

Some thoughts on surface repair fillers:

While fillers with opaque components (including wood dust) can be retouched to disappear at one angle, they tend to stick out like a sore thumb when the viewing angle or lighting angle changes, since they don't conform to the same light-handling properties as the underlying and surrounding wood.

Jerry Lynn's and Jeffrey Holmes' (in the linked thread) suggestions for using scotchlight s22 or aluminum hydroxide are really good, since they are semi-transparent, allowing the light-handling properties of the underlying wood to come through.

Another advantage of using these inert mineral-based components in either a glue or varnish-based surface repair filler is that the more mineral content you can get away with, the less shrinkage there will be. Filler varnish by itself tends to shrink a lot, and for a long time. Ideally, with enough added mineral content, the resins alone will not be the main thing taking up the space, but will only be acting as a binder for the minerals, so swelling and shrinkage will be greatly reduced.