Official Luthiers Forum!
http://w-ww.luthiersforum.com/forum/

getting nice smooth final coat of shellac
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=6718		 Page 1 of 1
Author:  ecklesweb [ Tue May 16, 2006 1:30 pm ]
Post subject: 
I'm using shellac to finish a guitar I'm working on. This is the first time
I've used shellac (for any purpose). I'm using a 3 lb cut of amber shellac,
and I really like the results so far with three coats. However, in the light I
can see that this last coat isn't just perfectly smooth - there are some
areas where there's a little more finish that others.

One choice obviously is to buff it out with some 000 steel wool, but I like
the luster that the finish has at this point and I don't want to lose that. I
suppose I could wax over the shellac to get the shine back after buffing
down to a satin with 000 steel wool, right? (I don't have the patience to
learn french polishing right now!)

I wonder if there's an application technique that would help. Right now
I'm wiping on the coats with a cotton cloth. I've done some test pieces
with a nylon brush and I'm not as happy with that. Another thing I have
to admit is that I haven't tried diluting the shellac to a 2lb or 1.5 lb cut. I
have some blond shellac in a 2lb cut, should I try that as my final coat?

Any tips?

Thanks,

Jay
Author:  hoosierukes [ Tue May 16, 2006 1:34 pm ]
Post subject: 
It's all here...
Author:  tl507362 [ Tue May 16, 2006 3:19 pm ]
Post subject: 
Yes! Start thinning your shellac as you get to the last coat. These thin coats will melt the finish under it and help level it with the french polish technique. This will give you a mirror finish. Then finish off with some Plastic Polish #2. It'll look like glass! Good luck. I'm sure Michael will chime in shortly, he's the go to guy for FP.
Tracy
Author:  Michael Dale Payne [ Wed May 17, 2006 1:35 am ]
Post subject: 
So I gather your doing a ragged vs. French polish application. Meaning using just a cloth and in straight strokes. this is OK but is hard to build consistant depth of film this way because the shellac is wetter at the start of the stoke and dryer at the end. you really should change to working with a 2# cut to build the film up and then finish with 1# cut. Ragging will not complete as a smooth final film with out spriting off and maybe sanding to level and finaly polishing with a polish agent like perfectit or Mcguires #7

French polishiing on the other hand will produce a more consistant film depth and if done with great care will need no sanding or polishing to complete.
Author:  Michael Dale Payne [ Wed May 17, 2006 4:00 am ]
Post subject: 
A short little tutorial on how I spirit off and the keys to not pulling of shellac.

First and foremost keep in the back of your mind that by adding alcohol to the pad ( the muneca) is that you are cutting the residual shellac in the inner pad , not flooding the pad with alcohol. You want the muneca to be just barely wetter than if you were boding.

Next the stoke should be with the grain. This will lessen somewhat the tendency to pull off shellac. Also the force of the stoke should be firm but the motion quick. So it is a compromise between how hard you press and the ability to stoke quick and constant in a straight line without sticking or dragging.

I find it helps to keep in mind the purpose of spiriting off. During the building of the film stages it is mainly two fold. It is to remove residual oil and to level the last body session. During this stage less pressure and a slower stroke than in glazing is required and the film should not be over worked. This one of the biggest cause of film removal (over working). Be sure to keep your muneca properly loaded. Too dry and you stick thereby removing film and to wet over melting the film thereby removing film. We just want to barley melt the high ridges of the previous body session. (I hate the word layer when referring to French polish because you are actually build a single amalgamation of shellac not stacked layers)

In polishing out or otherwise known as glazing you want to load just a single drop of oil to the muneca this to aid friction resistance and spread it around on the muneca face. Use more pressure and faster strokes. This is like buffing shoes polish and is a process that is accumulative. The glosser you want the surface the more glazing required. Here again keeping the muneca properly loaded is key

In both types of spiriting you need to glide onto the starting edge and glide off of the trailing edge in a smooth constant no hesitating motion. This motion is an other key to not removing film
Author:  ecklesweb [ Wed May 17, 2006 1:56 pm ]
Post subject: 
Michael, I'm taking your advice from your first post - I'm sanding level
(with steel wool) and then polishing with an auto polish. I'll have to
check, but I think McGuire's #7 is actually what I picked up. I tested this
on some scrap and I'm pleased with the results. I'm just looking for some
luster, not a mirror finish like a french polish.

Thanks for the advice!

Jay
Author:  gburghardt [ Wed May 17, 2006 3:07 pm ]
Post subject: 
French polish hasn't been as hard for me as I was led to believe. The link that Geoff Davis (NIce name Geoff!) posted really helped me a lot. Another helpful source was Robbie O'brien's guitar finishing DVD. He goes over a very simple and effective french polishing schedule and you could steal the last few steps from where you are (since you've already brushed on the bodying coats) to get to the final finish you want. Good Luck!

geoff
Author:  Michael Dale Payne [ Thu May 18, 2006 12:32 am ]
Post subject: 
French polish is only as hard as you make it and you can French polish to any sheen you want from flat, satin to high gloss. French polish is really not a finish luster but rather a technique of apply the media. I know some that brush on to near depth, sand level then only French polish the final 2 or three body sessions. I have done jewelry boxes that only had two sessions and a coffee table that had 40 body sessions. There are as many different custom techniques as there are rain drops but the basic process is a padded-on in circular motion application of shellac. When you boil all the mystery out of it that is what it boils down to. As Simple as it sounds, depending on what technique you use there are nuances to learn and master and the more you do the better you get. The thing that I believe scares most people about the process is the work involved. It is not a finish you can walk in and apply a coat in 5 min and walk away till time for the next, that and some elbow grease is required. Personally I find it meditative Last but not least it is the fastest finish from application to ready to go, and sonically the least dampening.

I truly feel that every Luthier should have this in his arsenal of skills. I also believe it is one of, if not the best beginning finishes for new builders because how well it teaches the basic of fine finishing, with a high first time success rate, due to its ease in reparability.

If you’re the kind of person that likes to work a process and watch it develop before your eyes! Give it a try. You may find it as an escape as I do
Author:  gburghardt [ Thu May 18, 2006 2:20 am ]
Post subject: 
Jay,
I forgot to mention that since you mentioned you haven't worked with shellac before, beware that it sands much easier than laquer. I would suggest beginning your flat sanding with 1200 and move down if it is not getting the job done. But I have tried to flat sand shellac beginning with 600 grit before and by the time I got to 1200 I had gone through in many places (also a symptom of not having built up enough). But, beware!
Author:  SStallings [ Thu May 18, 2006 7:09 am ]
Post subject: 
I'm far from an expert and had a lot of help from the people here but the most important thing I've learned is how little shellac/alcohol/oil you really need to put on a coat.
Author:  Michael Dale Payne [ Thu May 18, 2006 7:27 am ]
Post subject: 
Lets assume you have residual shellac in the inner pad of your muneca. My typical fresh load up is 5-6 drops of 2# cut shellac, 2-3 drops of Alcohol and 1-2 drops of oil. Now this varies a good test is after tapping the muneca on a white piece of paper it leaves an intermittent print somewhat like a finger print then it is about right for boding. If it is a solid print it is too heavy. If there is nearly no print in the middle it is too light. The Milburn tutorial in the reference section has a good photo of this test. Then when working if you see the alcohol cloud appear and disappear about 1” behind the muneca you have the alcohol right. If you have a wet streak that turns to dull longer than 1 ?” or more behind the muneca then either you have too much shellac, alcohol or oilMichaelP38855.6860532407
Author:  nickton [ Thu May 18, 2006 9:21 am ]
Post subject: 
   I tried it after downloading the instructions from the bob and orville melborne site (linked to above). An incredibly tedious process but also rewarding. I got to the glazing stage I think and decided to use some nitrocellulose I had also bought to make a stronger finish, and also to get some experience at that too. It's an expensive overkill but I must say my ideas about finish have been much upgraded. Before this I'd use Tung oil or Deft Oil usually on furniture and box projects, and liked them. But this is a whole other world. I'm sure it will take a long time for the guitar to fully cure..(like maybe a few years)...But I wanted to learn both ways.   This was definitely the most time consuming process on this my first guitar... Like 2 or 3 weeks I think. Still not really done with it. I liked using rottenstone even on the laquer I noticed, after wet sanding up to 1000 grit. Grain filling with pumice was a bit of a pain.nickton38855.7703240741
Author:  Michael Dale Payne [ Fri May 19, 2006 3:38 am ]
Post subject: 
I use Zpoxy finishing resign for grain fill even on French polish.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/