Official Luthiers Forum!

I've been meaning to do a proper test of Pre-cat before using it on a gloss guitar, so over this past weekend I ran a test piece through the following sequence.
Before I begin-one bit of clarification. I use Sherwin Williams products. I don't have any particular affection to this brand, they are simply the materials that I can buy locally and I have a factory trained representative at my disposal who knows the entire product line, it's compatibilities with other components such as dyes, stains and solvents, and can custom mix or match colors of dyes & stains. I firmly believe in using a single manufacturers system from start to finish. I've had problems (fisheye, checking, etc.) when "mixing and matching" brands and types in the past. I am not qualified or interested in comparing with any other brands, as I have not personally used any.
I used #T77F57 High Solids Water White Clear lacquer, Vinyl Sealer # T67 F3, catalyzed at 2% with V66V26, and # R7K120 thinner an needed. If you're using a pre-cat finish you must catalyze the sealer. The shelf life of 1 gallon of the pre-cat is about 6 months, which is a lot of guitars, so I'll schedule with other furniture project. This is probably not a cost effective way to finish one at a time guitars.
The sole advantage of this finishing system is the 2-3 day turnaround time from bare wood to polished and done.

First I sent a piece of 1/4" Finn Ply through my drum sander with 180 grit abrasive to achieve a uniform thickness. The actual thickness is arbitrary, on account of I'm only concerned with the amount of increase (the film thickness) I checked the thickness on all edges and ends (in about 8 places overall. I noted the initial thickness on the back. My sander is accurate to .002 or so.
Then I shot one wet coat of Vinyl sealer & let dry for 2 hours. Lightly scuff sand with 320 grit.
Next shoot 3 wet coats of Lacquer thinned 10% allowing to dry 1 hour between coats. The first coat would be where any tint or sunburst would go on. I have a "incubator" set up to dry guitars & parts in. I get the temperature up to about 80º in there with a single 150 watt heatlamp for the 1 hour dry time. After that the heatlamp (and small exhaust fan) goes off and it settles down to ambient shop temp of around 65º. You can force dry this finish at 120º and shorten the dry time considerably, but I wouldn't do that to a guitar...
Allow to dry overnight.
Lightly scuff sand with 320 grit on the ROS.
Shoot 3 more medium wet coats @ package strength (no thinner) allowing 1 hour dry time between coats.
Allow to dry overnight and the following day.
Level sand with 600 grit, then 1200 grit, then a 2000 grit Abralon, all with the ROS.
Buff with Menzerna Medium grit on the canvas buffing wheel, then Fine grit and a flannel wheel and you're done. This lacquer buffs very easily and very well.

Final measurement is .004- .005 final film thickness, right at the Manufacturers limit.

-C

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Freeborn Guitars
and home of BeauGuard©

Interesting stuff. How does this compare to other finishes in terms of thickness? Poly, FP Shellac, Tru-Oil? Anyone else done this type of research?

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Time is a great teacher, but unfortunately it kills all its pupils - Louis Hector Berlioz

Chansen / C hansen / C. Hansen / Christian Hansen - not a handle.

Christian

I just finished a guitar using the Cambell's Eurobuild cat urethane. I filled the pores with z-poxy, sprayed two seal coats and then the topcoats. After leveling and buffing I took it to the store and used their ultrasound to see how thick the finish was. It was consistently between 3 and 4 mils. Anything less than three and you are getting close to a French polish in thickness.
BTW, the data sheet on the product says to spray between 6 and 10 mils. hahahaha, yeah right!

Robbie, I am looking for something more durable than the McFadden's nitro lacquer I am currently using. Hope you don't mind a few questions:

Does the Eurobuild burn in?
How is it for sanding and buffing?
How long did you let it cure before buffing?
Are you pleased with the results?

Any other impressions/comments would be appreciated. Thanks

Barry,

The product I used on this last guitar was from M.L. Campbell and is their Eurobuild catalyzed urethane product. It comes in several sheens and I used the "wet look". The mix ratio is 2:1. I have used their gloss sheen in the past which doesn't require a sealer as it is self sealing. The wet look requires the sealer. These products are post catalyzed, meaning you add the catalyst at the time you are ready to use it. Once the catalyst has been opened the left overs have a very short shelf life.
Also, this is not an evaportaive product like regular lacquer. In other words, it will build in layers instead of burning into the previous one. There is definitely a learning curve when going from an evaporative product to a reactive one so consider this if choosing this type of product.
With this type product you can usually finish a guitar in a week or less. I have even sprayed one day and buffed the next. However, at least a couple days of cure time gives better results.
I used their sealer under the topcoats and it sanded very nicely. Even the topcoat sands back easily between coats and is easily leveled/buffed.
In my finishing DVD I talk about catalyzed urethanes and even give a resource of where to buy from a company called ILVA. This is an Italian company that sells through Camger here in the States. This is a self sealing 2 part urethane post catalyzed at a 1:1 ratio.
Either product will work but I am partial to the ILVA brand.
I hope this answers your quesitons.
Happy Finishing!