Shellac finish repair

[Paul-in-Plymouth]

I have some questions for the shellac experts.  We have a hard-maple drop-leaf dining table that my wife’s father made for her mother as a wedding present some 75 years ago.  It is finished with blonde shellac.  When it came to us about 10 years ago, the finish on the top surface showed some deterioration.  At that time I removed the old shellac from the top and refinished with fresh blonde shellac to match the rest of the table and the chairs.  Recently, the top sustained a long, but shallow scratch.  

As far as I can see with a hand lens, the scratch is contained within the shellac layer and does not extend into the underlying wood.  So, in principle, I should be able to fix the damage with some more shellac to fill the scratch, then polish out.   But then come the details.  Two main questions:



1.  I don’t want to entrain porosity or undissolved fragments of the old shellac, covered up with new shellac.  That tells me I should start with a dilute cut or even straight DNA to clear out or dissolve the loose material in the crack.  Does that make sense to the experts?

2.  I still have some of the old, made-up shellac from when I refinished this piece in 2008.  It was unopened until last week.  It dries hard on some test pieces and seems to work fine.  I also have an unopened, newer packet of flakes from the same supplier and could make up a fresh batch.  So, I have the specter of deterioration of the old solution (though it seems OK) versus the (imagined?) possibility of lot-to-lot variation in color if I make it up fresh.  

Thoughts and advice would be appreciated.

[jteneyck]

I think you'll be OK with regards to Q1 by just brushing the scratch and vacuuming to remove debris.  Anything still there is stuck well enough and will melt into the repair.  With regards to Q2 it's your call whether or not to use the old shellac.  If it dries hard it should be OK, but 8 years is really old for any premade shellac to still be good. 

With respect to the repair process, I would apply new shellac with a fine artist's brush to fill the scratch.  Start with DNA if you want but I don't think it's necessary.  It will take several coats.  When you are done you want the repair to be proud of the undamaged surface.  Make sure the repaired area is higher even if your last coat or two spills over a little.  Let that dry/cure for several days to get really hard.  Then wet sand it with 400 or 600 grit using MS as a lubricant until it's flush with the rest.  Then pad/wipe/spray a finish coat to the entire surface.  

John

[Paul-in-Plymouth]

John,
Thanks for pointing me back in the right direction.  I’ll make up some new mix.  I’d hate to get part way through this and find the old stuff didn’t get hard enough or do something goofy.  I appreciate the advice.

Paul