French polishing

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limehills
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French polishing

Post by limehills » Sat Apr 13, 2019 10:56 am

Alright so a while ago I posted about having problems with cupping on this mahogany dread. It has stabilised quite nicely and I've had no more problems since.

I've started french polishing it and it's had around 40 coats of shellac so its coming up nicely. But I was wondering if anyone had some advice on how to get the shellac to have a smoother appearance, I've noticed it has vey fine streaks in the finish from where the polishing rag has applied shellac, they are hardly there and barely visible but still noticeable. I've grain filled the mahogany so there is no problems there. I've also been applying the shellac very thinly to avoid squeeze out and runs. Anyone else had this same problem or know how to fix it?

Cheers Laurence
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Laurence.

Petecane
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Re: French polishing

Post by Petecane » Sat Apr 13, 2019 7:42 pm

Looks beautifully done to me!
Superb polishing.
Pete

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kiwigeo
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Re: French polishing

Post by kiwigeo » Sat Apr 13, 2019 9:26 pm

Traditionally a spiriting off session after every few bodying session takes care of the ridges. There's a bit of skill involved in spiriting off so I take the easy option and I generally do a cut back session with 600 grit wet and dry wrapped around a felt block with a bit of oil for lubrication every few build sessions. This knocks off the ridges. What sort of material do you have on the outside of your muneca?
Martin

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Re: French polishing

Post by Petecane » Sun Apr 14, 2019 7:18 am

I also avoid spiriting off due to wimping out but use 2000 wet and dry with a touch of linseed.
Your polish mixture " could" be too thick?
I have learnt that it is better to keep the mix ultra thin.
Just my two pence.
Pete

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kiwigeo
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Re: French polishing

Post by kiwigeo » Sun Apr 14, 2019 1:52 pm

For the record I use a 2lb cut for bodying sessions and go to a lighter cut (1-1.5lb) for the last few sessions. I use hard shellac ready mixed up by Shines. If youre using this stuff keep in mind that you cant allow long periods between bodying sessions as the stuff will have started cross linking and will go goopy on you.
Martin

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Re: French polishing

Post by johnparchem » Mon Apr 15, 2019 12:14 am

In the pictures it looks pretty good. I mostly like to leave the finish looking off the pad so that people will know it is french polished, I have no ridges when I am finished but it is a different look than leveled with sandpaper (which also looks very good).

I do three wash coats (just pad it on) with a 2 lb cut, after that I use a 1 lb cut. I do not mix alcohol on the pad when bodying. I just use the 1 lb cut. I've seen see some techniques where a few drops of 2 lb cut and a few drops of alcohol are placed in the pad, so I figure I am just pre mixing. I also use a little olive oil. With a 1 lb cut I can continuous work a top for hours without the finish getting too soft. When I use a 2 lb cut straight on the pad the top gets sticky fast.

I do spirit off with just alcohol to remove oil and burnish the finish every few sessions. It is a touch thing but not really hard. When I spirit off I start with a fairly wet pad, the trick is no drips and one should not see visibly wet areas while wiping. So I start with a very light touch and incrementally press harder as the pad gets dryer. I am continually watching and feeling what is happening as I do with the grain strokes. By the end of a spirit off session I am pressing hard enough that I am careful not to crack the top. Two things can go wrong the first, leaving too much alcohol while wiping, a subsequent wipe after that can pull the build right off, the second is actually worse with the pad wet if you bump the edge of the guitar you may send a drip down the adjacent surface; no problem if wiped right a way, but if left it can ruin the FP on that surface.

limehills
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Re: French polishing

Post by limehills » Wed Apr 17, 2019 10:49 am

Thanks Pete I appreciate it.

And I haven't been spiriting it off just sanding it back to get rid of ridges. I also haven't been using oil mainly because the thought of putting oil on doesn't seem right to me, maybe that's why it isn't as smooth as it should be? I've also been using a 1 pound cut that hasn't been diluted, maybe I should mix it with a little more spirits. Lastly I've been using an old t-shirt with cotton balls in it to apply the shellac.

You can probably tell I'm new to french polishing so any advice I can get I appreciate so thanks for replying.
Laurence.

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kiwigeo
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Re: French polishing

Post by kiwigeo » Wed Apr 17, 2019 11:49 am

French polishing is something you get better at the more you do it. There's no one method...you try different techniques and you end up adopting what works for you.

limehills wrote:
Wed Apr 17, 2019 10:49 am
Thanks Pete I appreciate it.

And I haven't been spiriting it off just sanding it back to get rid of ridges. I also haven't been using oil mainly because the thought of putting oil on doesn't seem right to me, maybe that's why it isn't as smooth as it should be? I've also been using a 1 pound cut that hasn't been diluted, maybe I should mix it with a little more spirits. Lastly I've been using an old t-shirt with cotton balls in it to apply the shellac.

You can probably tell I'm new to french polishing so any advice I can get I appreciate so thanks for replying.
Martin

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auscab
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Re: French polishing

Post by auscab » Fri Apr 19, 2019 8:20 pm

:gui Hi .

Ridges and lines being in your finish is not yet understanding how thin your mix must be at this stage of bodying or finishing off.

As your trying to fill the grain and get a flat finish with each body it doesn't matter because a good cut back with fine paper with a solution to stop the paper clogging up flattens it off. I use a mix of linseed oil and mineral turps.

After the third or fourth body , if your good at it, the grain of the Mahogany should be flat and full . Your top should be done sooner because of no open grain .

After that the shellac should be made a lot thinner. Like take an egg cup of what your using and tip it in a Mug of metho . Ten times more metho than before .

Pro polishers take it down in stages as they head towards the end and finish off with pure metho taking off the oil at the end for a highly reflective finish.

Shellac finishes is all about keeping the finished product it as thin as possible . A full grain with a fine, no ridges end job is what look the best .
Aim for three or four bodies with a few finishing off stages with oil.

Rob

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Re: French polishing

Post by kiwigeo » Fri Apr 19, 2019 8:34 pm

Hi there Rob..it's been too long since we heard some expert words from you on finishing. Hope you're well and look forward to a few more posts from you in the near future.
Martin

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Re: French polishing

Post by auscab » Fri Apr 19, 2019 9:23 pm

Hi Martin .
Thanks :D .
I'm good . Ive been dropping in for a look every once and a while.
Rob

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Re: French polishing

Post by Petecane » Sat Apr 20, 2019 11:36 am

Rob is the one!
Keep rubbing back and keep it thin.
Pete

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Re: French polishing

Post by Petecane » Sat Apr 20, 2019 11:55 am

Ps..
I am not professional but for the record I no longer use cotton wool enclosed in a square of cotton because I cannot control the amount of polish to the cotton wool.
I also find that the cotton wool after several runs goes hard and therefore even more difficult to gauge the polish application.
I tend to seek out a well worn pair of 100% cotton knickers and form a " rubber " and apply the polish direct.
My old carpenter friend told me to then put just a finger full of linseed to the pad to help the polish spread without sticking.
So that's what I do.
I renew the pad as I approach finish.
For what it's worth?
Pete

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kiwigeo
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Re: French polishing

Post by kiwigeo » Sat Apr 20, 2019 12:51 pm

My munecas consist of a core of upholsterer's wadding and the covers are trace cloth (lint free). To stop the pad going hard I keep my munecas in a sealed jar. As far as oils go I've tried them all but of late have been using mineral oil.
Martin

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Re: French polishing

Post by Petecane » Tue Apr 23, 2019 11:58 pm

I have looked again and again at your wonderful French Polishing.
I have another side to this!
I think you are trying too much!
Your guitar looks glorious.
My take on this.
I harp on about this but in the sixties when I played a 1933
Santos Hernandez Flamenco guitar ..
It was not glass finished but so subtle.
You could just see the wood.
It was a sort of vinyl Matt.
There was a gloss but it was subtle .
Could have been the thirty years difference.
But I do not think so.
The guitar was coated very thinly with a form of Shelac.
I believe wood is wood and should be wood!
To see it, to love it, to play it and let it breathe?
You know what?
Rub the whole caboodle down with 2000 wet and dry and then polish it up.
Pete

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matthew
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Re: French polishing

Post by matthew » Mon Jun 24, 2019 10:40 pm

This thread is a little old but i just read through and want to add that the main lubricant we use in the workshop here for cutting back and for French Polishing with hard shellac ... is kerosene. It behaves like a very light oil and evaporates slower than the alcohol so it is a good lubricant. But, it evaporates completely and doesn't leave an oily residue like olive, walnut, mineral or other oils.
I also use a 50% kerosene 50% alcohol mixture (carefully) for cleaning and reviving FP finishes. The alcohol reactivates any shellacs there and dissolves rosin etc, and the kerosene stops things sticking. The alcohol is gone before the kero evaporates.
YMMV.
My FP process is wiping on straight hard shellac from the bottle with a muneca. I do this without going back over the strokes, just overlapping a bit. I might apply 3-4 coats like this. Then I cut back with 600 W&D and kerosene. Then I use a clean muneca and a more dilute shellac mixture with a little kerosene lubricant and french polish. I use cotton gauze bandage inside the muneca and clean white tee-shirt material on the outside.

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kiwigeo
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Re: French polishing

Post by kiwigeo » Tue Jun 25, 2019 7:10 am

matthew wrote:
Mon Jun 24, 2019 10:40 pm
Then I cut back with 600 W&D and kerosene.
WD40 is largely napthalene isn't it?
Martin

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Re: French polishing

Post by matthew » Tue Jun 25, 2019 7:29 am

oil and kerosene i think not naphtha.

some use wd40 but i want to avoid oil residue

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Re: French polishing

Post by kiwigeo » Tue Jun 25, 2019 8:04 am

Whoops....misread "W&D" as WD40. Time to head off to Specsavers :?
matthew wrote:
Tue Jun 25, 2019 7:29 am
oil and kerosene i think not naphtha.

some use wd40 but i want to avoid oil residue
Martin

asgilbert
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Re: French polishing

Post by asgilbert » Tue Jun 25, 2019 12:09 pm

Hi,

Pablo Requena has just finished a great series on french polishing which covers most of the questions I had on the issue very well. You might want to take a look.

https://www.youtube.com/watch?v=Uf4z14Vjkxk&t=1222s

Andrew

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