Low temp finishing & shellac questions

[Mike Crabbe]

I'm one of those people who does (almost) everything in the (unheated) garage. This time of year in NJ it's cold in there: 40 - 50F (I get some heat by virtue of the attached house).

I'm ready for the finishing stage for my guitar build and plan to brush KTM9 (I've only used this in warmer weather). So far I havent seen any specific temp ranges suggested and wondering if you all might have some suggestions about lowest advisable temp. (I suspect I'll need to either go inside ...or wait a couple months)

At the risk of including a second question - I have the LMI water soluable pore filler and plan to use that. Because I dont want the pore filler to stain the wood (just fill the pores), I would apply a seal coat first. (Spruce top, Mahgany neck, EIR sides and back, maple binding) In the past with mahogany, I just used the KTM9 as the seal coat and them applied the pore filler. Would there be any advantage to using shellac instead, or in addition, for seal coating? Will the shellac improve "wet" appearance of the wood? (I imagine it would add some warmth to the top) Does EIR require something other than KTM9 due to its oiliness? (I havent used it on rosewood)

Thanks!
Mike

[Neil Frost]

Mike - Just finished the same spec guitar as yourself - EIR and Maple Binding using KTM-9 padded on with a French Polish pad.

Three good lessons learnt

1) When it says stir before application - it means every time. As I got nearer the bottom of the pot the sediment was quite thick so I gave it a good belated stir and all hell broke loose - milky white finish and it does not rub out. The chemical soup had been effectively re-organised - game over. Up to then the finish was great.

2) Shellac is a good idea with oily woods. There is a technique that UK Luthier Adrian Lucas recommended for grain filling that works really well on dark woods. I was using conventional fillers and kept getting white dust filled pores when sanding back. He is a French Polish man and they simply do one coat of Shellac then using a lint cloth pad dipped in Alcohol/ Meths. The pad is rubbed with Pumice stone dust which is then worked into the wood as a slurry. Work on small areas at a time and wipe off quickly with a rough rag and move onto the next section. The oil from the Rosewood is leached out by the alcohol and this stains the pumice so well that is sands a dark colour. May need a second going over but it dries very fast and is well worth the effort. I did my sides without filling and there are still some pores visible after 12 coats of KTM-9.

And yes - move inside. Cold weather and finishing do not mix. Shellac and water based finished don't smell up the house. Just do the sanding off in the garage.

Hope that helps.

3) On your next guitar like this, do the filling and a couple of initial top coats before routing out for the Maple binding. Saves rosewood juice stains.

[Chuck Tweedy]

"3) On your next guitar like this, do the filling and a couple of initial top coats before routing out for the Maple binding. Saves rosewood juice stains."

I would definitely recommend sealing the binding ledges to keep the "rosewood juice" at bay - However, pore filling and starting your clear-coat build prior to installing binding can be a recipe for some pain.
Frequently - if not always - the sides get scraped and sanded quite a bit in bringing the binding level with the sides. At which point your clear coat will be gone, and likely you will have to do a whole lot more pore filling.

To keep "rosewood juice" from fouling your maple bindings (I really like that "rosewood juice" thing
I recommend sealing the ledges (as said before), then after everything is level, sealing the binding again - too keep-out both pore-filler stain and rosewood juice.

Yea! I got to say it again!