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Between students over the last couple of months I have been working on some more Royal lac sample boards for Vijay at Shellac Finishes.
Here are some pics as well as my finishing schedule and observations.



O’Brien Royal lac spray schedule - Sample boards done at the request of Vijay at Shellac Finishes
Application method: Spray can and spray gun


Day 1 – Pore fill rosewood with shellac and sawdust

Sprayed spruce and rosewood both from rattle can and with spray gun. Sprayed 3 very light coats at 5-10 minute intervals. The rattle can sprayed better out of the can but the spray gun had a bit of orange peel because I didn’t thin it.

Day 2 – Lightly sand yesterday’s samples with 320. Sprayed 3 more coats at 1 hour intervals. Due to operator error the first coat of the spray can spit on the surface but it looks like it will sand out. I went ahead and did the 2nd and 3rd coats over the spit marks. I still sprayed with the spray gun at full strength. Increasing the pressure seemed to help a bit with the atomizing. The coats I sprayed were medium to heavy coats. I will let the pieces cure for a while now.



Day 3 - I let the first two days' coats cure for 2 weeks. Today I sanded and noticed that with P600 there was some gumming of the paper. When I used P320 I had no problem. I applied three more light coats at one hour intervals. Weather permitting, I will level and spray again tomorrow. This should conclude the build coats. I will let it all cure some more and then try and spray thinned final coats. I am a bit worried about getting enough build on my final coat to be able to level and buff without going through it.



Day 4 – I got busy and was only able to get back to the boards after two weeks. Today I leveled with 320 and then sprayed 3 light coats at one hour intervals. After one more hour I sprayed another coat but went over it immediately with an additional coat, so maybe one heavy coat or two light coats. I thinned the royal lac sprayed from my gun at about 20%. Looks like I have enough coverage so now I need to wait 3 to 4 weeks in order to level and buff. Coverage appears to be very thin.



Day 5 – After 3 weeks I leveled and buffed the boards. I started with 1000 grit but this stuff is really hard so I dropped it down to 800 wet. I then went back to 1000 wet and then buffed on a buffing wheel with fine grit Menzerna dry compound. I also rubbed some out to satin using steel wool and my Lutherie wax after having leveled to 1000 wet.



Conclusion and observations:

Hardness: This stuff is hard! It will definitely offer protection against scratches, heat, moisture, alcohol etc. It is very thin and in my opinion will not offer dent protection.



Shrinkage: I expect it to shrink back over time just like I would expect from any other finish. I finished a bird’s eye maple guitar over a year ago with Royal lac and some of the grain lines are telegraphing though the spruce top. It is similar to a lacquer type finish. It still has a high gloss though like it just came off my buffing wheel. The finish has shrunk into the bird’s eye maple somewhat but I would expect this also from any other type finish. I did no pore fill or sealing on the maple before finishing. Perhaps an epoxy fill would eliminate this. Once again though the gloss is brand new.



Application: It was very easy, especially from the spray cans. I feel I could easily do a complete guitar with a couple of the spray cans. I think it even sprayed better than using my spray gun but there are a lot of variables using this method of application. I did find that thinning the final coats help a bit.



CA GIue: I dropped one of the spruce sample boards on day one and of course it cracked. So, I repaired it with CA glue and sprayed over the crack. I learned that you can use CA glue under this finish for leveling/sealing/pore filling etc. without issue.



Appearance: The appearance is very clear and the high gloss is exceptional. It looks very “ full” although the final finish is very thin.



Touch up: You must re-coat an entire area rather than doing spot fixes.



Cure Time: Do not rush this stuff. It must cure completely in order to form a strong molecular bond. I would treat it like lacquer in that respect. Give it a good three to four weeks or longer if possible.



Solids Content: I was using a version that had 26% solids in the formulation for my spray gun application method. I do not know what the spray can solids content is. I have also used the 21% solids recipe and found little difference between the two.

Thanks for sharing findings.

Robbie,

Thanks for the info. Great stuff. I'm becoming a fan.

I'm wondering if the test for shrinkage might be better served using wood with more homogeneous grain, such as a rosewood or ebony, since spruce is known to shrink over time, even absent changes in humidity.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

You are correct. I have noticed more "shrinkage" on spruce but this is probably just the wood itself moving and shrinking under the finish. I have rosewood sample boards that are over a year old and they look just like the day I did them.

Here are some more sample boards I just finished using a new low VOC recipe that Vijay has put together. On these I brushed, padded and sprayed. I was really impressed how the product went on with just a natural bristle brush. It flowed out nicely, dried quick to the touch and leveled and buffed easily to a super high gloss by hand or on a buffing wheel. If you are looking for a finish that can be applied with a brush this is definitely it!
All of these sample boards were done on spruce so no pore filling required. I sanded to 320 grit and then applied the finish by either wiping it on with a rag, brushing it on or spraying it with a spray gun. I made it a point to spray fairly heavy coats with my spray gun to see how it would act. After 4 weeks of cure time I leveled and buffed and got the results you see in the pics.
I am also including a pic of a bird's eye maple classical I finished with Royal Lac over a year ago and it still looks like new. This finish was just wiped on with a rag like I show in the video I did for Vijay.