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Hi guys
I am in the middle of my second french polished guitar and am experiencing the same problem.
I have completed about 5 bodying sessions and am getting a really nice shine. However, little checks are appearing on the surface. These come out as tiny little pin holes.
I am following the Milburn tutorial. Am I experiencing the 'crazing' that they talk about??
I do one body session a day so the finish has definitely had time to harden.
On my first guitar I got rid of the small cracks by levelling and glazing.
Any ideas on what I can do about this.
Many thanks
Mat

Just curious as to the wood you're french polishing over and what kind of shellac and is it fresh?

I've done about 10 guitars now this way and haven't had this happen but there is a first time for everything. Best of luck.

SR

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"We might not be big but we sure are slow"

I guess that you need to just try a new shellac batch - buy new shellac and alcohol, Everclear type is best, and fresh Extra virgin olive oil, if you think you follow the Milburn method well. It doesn't need to be followed religiously, you will feel yourself when you add enough shellac, enough alcohol, enough oil... But as a rule of thumb, only add a little of everything and not often - as long as it doesnt drag or stick, don't add more, just rub and rub until wits end - also push it well - it is important for melting the stuff together and spreading it well around. Until I regulated the pressure feel I sometimes pressed so hard I burned throu the finish down to the wood. This can also happen if you run it too wet with too much alcohol. Better work dry and if it sticks, you can easily level with 1000 grit paper and oil.

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Build log

Crazing and checking is a shellac issue or contamination issue. of all the years I have French Polished I have never had crazing during the application. Something is a problem with your shellac cut.

As far as one body session a day. Why? Ten to fifteen minutes is more than enough time between body sessions. I know Milburn tutorial did not tell you to do only one body session per day. The intent of this type of application is to amalgamate or melt each session into the previous session. build on continious film. Not to build hardened layer over hardened layer. With proper technique it is reasonable to apply as many as 5 or 6 body sessions in full work day. And that includes spiriting and stiff off between each session.

Photos of the checking would help to diagnose what is going on.

Michael, could this also be a problem with the quality of alcohol being used? Just wondering what the implications of using hardware store denatured alcohol are.

I have to say I nave never had any issue with hardware store DA I have ever used, though I now use pure grain alcohol exclusively on French polishing.

That said there are so many compounds used to denature the alcohol it is more than possible. But you must understand that DA manufacturers know the most common use of their product is as a coating thinner and clean-up agent. It would not be commercially wise of them to knowingly add a known coating contaminate agent that will give their product a bad name. But you never know.

Most new finish crazing I have ever seen happen that was not cause by bad shellac actually was tractable back to personal hygiene products more often than you would ever believe. Hand creams and lotions, deodorant and aftershave.

Mat,
I would agree with Michael in that perhaps your shellac cut is off. My guess is that maybe it is too concentrated and you are building too fast, (at least at the beginning) and not enough spiriting off to level. Because as Michael and Alex explained, the shellac amalgamates to the previous film, don't expect a new layer to fill existing divots. In fact, the opposite tends to happen: imperfections tend to propagate as you build. I find that scrupulous surface prep is the key before French polishing and to pay particular attention at the beginning to imperfections that may be forming. It's always tempting to get out of the gates fast, but in the end it always costs you more time in the long run.

Checks and pinholes are two different things. Checks, or alligatoring, can be caused by oil entrapment in the film. In Spain, most guitar polishers use hair oil, i.e. the stuff to slick your hair back, which is just mineral oil and some fragrance and maybe just a bit of something volitale thrown in. The only time I had alligatoring was when I used "Tres Flores" hair oil, which is mostly mineral oil. Since switching to walnut oil I have had no problem. I surmise that the vegetable oils are less prone to entrapment than the petroleum oils.

Pinholes are usually a contamination symptom, with the film staying away from certain areas, crawling back if you will. Silicone is one such material to steadfastly avoid. Did you use no-load paper in the sanding of the wood process? I have heard that the stearates used in no-load paper can work their way into the wood. Once the wood is sealed, the stearated paper causes no problems.

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One more thing to look for that can lead to this issue is pad or outer muneca contamination. be sure to store and place your muneca in an area that it can not get contaminated. Also change outer pad as need when it shoes wear and discoloration. also if you washed your pad material to get it to desired openness fabric softeners in some detergents can be an issue.

Crazing is when the shellac separates and the contamiate agent forms micro channels or pools. As the film dries the solids shrink and the channels or pools become obvious. This issue is either in the cut of shellac of some form of contamination that is being spread around as you body.

And yes non extra virgin olive oil often contain fragrant and artificial flavoring that can be a contaminate. The term “extra virgin” means that no additives have been used. Now here is another issue and can happen with the cheaper extra virgin olive oil brands. Many producers press more than olives in their presses this to can lead to contaminates in oil that is so called extra virgin.

So where do all the problems end?

I have been using methol hydrate from the local paint store for my alcohol and Johnsons Baby oil. I use shellac flakes from LMI. I use a 2 pound cut, and have not had the problem that has been described here. I have only ever had one problem with checking. My furnace quit once when it was very cold...I live in Alberta...and it checked over night. I was able to repair the checking just by doing the next session.

I will only mix my shellac when it is time to start. Mixed shellac has a fairly short shelf life...could this mabye be the problem?

David Gilmore

Guys - thanks for your help
BUT i'm still not sure what to do. It is definitely 'pin holes' not 'checking'. The more I polish the more they appear! They will not come out on a camera so i can't show you the problem (they are miniscule but when you're working so closely you see every little blemish - and they are blemishes).
The shellac is freshly made (although the flakes themselves are possibly 1yr old). I used denatured alcohol from LMI. I use olive oil as a lubricant. The muneca is made from old t-shirt kept in an airtight jar.
I pore filled with Zpoxy and I also put Zpoxy on the top for colouring.
Should I try a different shellac?
Can I use a different shellac on top of the old - should I sand back?

Any more advice would be really useful - thanks. The overall polish looks lovely, just this stupid problem.

P.S. I cannot get denatured alcohol in England!! What do you English guys use??

Guys - thanks for your help
BUT i'm still not sure what to do. It is definitely 'pin holes' not 'checking'. The more I polish the more they appear! They will not come out on a camera so i can't show you the problem (they are miniscule but when you're working so closely you see every little blemish - and they are blemishes).
The shellac is freshly made (although the flakes themselves are possibly 1yr old). I used denatured alcohol from LMI. I use olive oil as a lubricant. The muneca is made from old t-shirt kept in an airtight jar.
I pore filled with Zpoxy and I also put Zpoxy on the top for colouring.
Should I try a different shellac?
Can I use a different shellac on top of the old - should I sand back?

Any more advice would be really useful - thanks. The overall polish looks lovely, just this stupid problem.

P.S. I cannot get denatured alcohol in England!! What do you English guys use??

Ok let start here before doing anything.

Did you sand back the Zpoxy to a point that there were no viods (pin holes) and a smooth surface or back to the wood surface leaving the Zpoxy only in the pores and not on the base surface?

Did you seal or wash coat the the guitar before starting boding?

Is you olive oil extra virgin?

lets clear these things up first then we will work our way forward.

In the mean time let me recommend tht you discard the t-shirt material and change to well worn linen of muslin as your outer pad. T-shirt material will work but is not near the best to use due to the ridged weave.

we can at this time take a drop of your current cut of shellac and place it on a clean piece of plate glass allow to set over night and then we will test the shellac cut.

After the shellac drop has set-up over night the first thing we will look for is if a pinhole of any form of channeling has happened to that drop. if not then there would appear no contaminate is in the shellac cut.

Next we will pres our thumb nail into the shellac to see if it is properly hardening. It should be the consistency of very hard taffy. it should take some force to drive your thumb nail into it. If it is more the consistency of soft taffy then the shellac is not hardening properly.

Michael - thanks for your help
This is the second guitar with the same problem but I have done them differently.

This one was with zpoxy - the other with pumice. I did not sand the zpoxy back to the wood (the reason for this was because after watching R. O'Brien's DVD he used zpoxy to 'colour' the top. I reasoned that because the spruce had no pore's he must be leaving a coat of zpoxy on the top before finishing. I therefore did the same with the back and sides).

I did not use a seal coat (because I thought the zpoxy would act as such). On the first guitar however, I did a 1lb cut as a seal coat.

I am using ordinary olive oil - not virgin

I am using old t-shirt because I read that that was a very good material to use?
Thanks
Mat

Bingo!!!!!! We have more than likely found the issue If olive is to be used it must be EXTRA VIRGIN any olive oil that does not say EXTRA virgin has been cut with a fragment, coloring or flavoring. Many of these are known to cause issues and do not dry or float to the surface properly.

T-shirt is a alright material and is normally available to most people without effort. however its weave is problematic in that it will trap abiant dust and dirt and then lay it on the film. it also imparts a fine ridge in the film while boding that muslin or linen do not. and the shellac does not flow from the inner pad through it quit as well as linen or muslin.

Yup. Several months ago, the New Yorker magazine had a long article about fraudulant practices in the Italian Olive Oil Industry...apparently it's rampant. They're combining hazelnut oil, etc to boost the profitability of "x-virgin" Italian olive oil.

YIPPEE!!!! I hope so.

I will try the 'good stuff' Michael and let you know.

Thank you for your help.

Mat

Good reason to switch to pure walnut oil

Lets still do the shellac test on plate glass just for good meassure

Michael - one more thing, sorry to be a pain,

As I already have the pin holes, should I sand back a wee bit before the next bodying sessions or do you think I could go right over them (they're not that deep!! lol)

Oh, ok.
We were writing at the same time
I'll do the test
Thanks

Let kill all suspects before we do any thing.

I hate with a purple passion ever touching a French polish finish wit any kind of abrasive. Not having a photo to judge by my fist reaction is to tell you to stiff off till the film is level. This is to be done in straight strokes with no added shellac (only the residual in the inner pad) load only with alcohol and one drop of walnut oil or high end EV olive oil, use quick firm glide on and glide off motion always from the same direction per session alternate the end you start at each session and start at the centerline and work to each side. Glide on at one end glide off the other. Never allow the pad to slow or stop. This process will melt and drag the shellac to level. If after 5 or 6 sessions you sill have the pitting (pin holes) then we will talk about sanding down or wiping off using alcohol as a solvent.

By the way, I know the Millburn tutorial states to spirit off or stiff off after every third session. But us old timers will tell you that if you spirit off after every session from the second session forward there should be no reason that you ever have to sand to level. The spiriting off process is intended for to functions. First is to remove the lube oil and the second is to level the film as you go. Both Colin and I never touch the film with an abrasive. We go from boding, spiriting or stiffing to boding till we reach thickness and from glazing to stiffing to glazing till we reach the desired sheen and never touch the film with sand paper.

A related question about "bad" shellac. I know once shellac is mixed with alcohol it has a limited shelf life. What about the flakes. If they are kept in a container, how long should they last? Do you have a set time and then throw them out? I'm getting ready to start finishing a guitar and I mixed up the last of a bag of flakes that are probably a year old. Am I safe or should I get new? Thanks.

With any natural resin or synthetic for that mater there is a shelf life. Be it flake or mixed. Dewaxed shellac flakes should last a long time if keep out of temp extremes and sealed against moisture. The thing is you only know when you received the flakes. You have no way to know when the flakes were processed. I have bought bad flakes; I have had flakes good for 3 years. If making a new cut I always do the glass test before I use the cut. But I pretty much do a test on any finish I use before application.