Problems with Tabletop French polish not drying properly.

[Grahamemes]

Hi, looking for some opinions from you guys. I have always mixed my own shellac until recently when I bought some fiddes Tabletop about 6 months ago, also I always used mineral oil but decided to give linseed a go at the same time, I polished one guitar and it didn't feel good, nothing felt right, I put it down to my change in oil and changed to baby oil (paraffin oil/mineral oil) so a few months later I come to polish another guitar and now I have finished it seems the shellac is not drying fully. To give an idea, It appears dry and if you brush your hand over the finish it is fine, but if you make contact with the finish for more than a few seconds it leaves an imprint. My process is I seal the guitar with a thin solution of shellac, then I grain fill with pumice and alcohol, then body up a few coats quite thick, all with a pad and no oil, and after each coat I cut back gentlly with superfine pads, and use a tiny bit of pumice throughout the bodying to help keep my layers flat. Then I use a few drops of oil as a lubricant when the pad starts to stick for a few more layers before spiriting off with a thin shellac solution.
I have spoken to a technician at fiddes who thought that it's probably the fact that I am using oiI and that Is stopping the shellac from hardening. He said that their Tabletop has a pretty indefinite shelf life so it's unlikely to be out of date which was my main thought, as I know of other people who use Tabletop solutions with oil and have no issues, and the way the finish is not hardening properly seems inline with things i have read in line with polish being out of date.
Also, the fiddes guy said that their Tabletop is basically just shellac and 99%ethanol with a tiny bit of melamine, so I don't see why it would react so differently to any other mix.
I feel fairly confident in my polishing and have polished a lot of guitars, so i am looking for opinions on this or anyone with similar experiences of please to try to get to the bottom of this.
Thanks in advance!

 

[woodbrains]

Hello,

I'm afraid the guy from Fiddes is wrong. Mixed shellac does go off and does have a shelf life. The alcohol and shellac forms esters over time, which are soft and gummy (they are plasticisers). The film finish is never as hard as freshly mixed shellac, and at its worst, the finish remains gooey.

Mike.

 

[Grahamemes]

Thanks Mike, I appreciate your fast reply there. That was my impression, and to be fair he Guy from Fiddes said he wouldnt trust it if it were a few years old bht thought that it should still be fine after 6 months if kept in a sealed container. It's been about 6 months now since I bought it, but I started polishing the guitar about 2 months ago so I would imagine it would still be ok as I built most of it up I n the early stages. As a matter of course I would not use my own mixed shellac after six months for anything other than maybe as a sealer, but I have head that it's not guaranteed to be bad after six months or so.

 

[Grahamemes]

Also spoke to a guy at the company I bought the Tabletop from and he said It must be that I used oil and in his 8 years he had never heard of anyone using oil with Tabletop and I got the impression that he thought it weird that I had. So maybe I'm going mad, but I've I only heard if a handful of people ever doing French polishing without the use of oil at some stage so I would imagine it normal to expect people to do so. I am making a test piece now without oil to see if it does indeed make any difference, but I am still interested in any other peoples experiences or views on the matter!

 

[woodbrains]

Hello,

Using oil to lubricate the rubber during French polishing is common, indeed, though I never use it. However, if there is melamine in the finish you are using, perhaps the oil is interfering with that. It could be that spiriting off the oil is not possible due to an impermeable film forming from the melamine addition. Pure shellac is micro porous and allows spiriting off.
I would never use mixed shellac older than a couple of months myself, though. If yours is 6 months old and factory mixed so we don't know how long it stood on the suppliers shelf it could be way past its best.

Mike.

 

[Grahamemes]

Thanks again Mike, that pretty much sums up what am thinking, damn why did I try something new lol! You could be right about the melamine although I did use a polish in the past which had melamine in it and had no problems with that, but that had other stuff in it too I think so maybe that somehow acts in a different way to the Fiddes stuff. I do find it strange that given it is so common for polishers to use oil that if fiddes are making a product that isn't compatible with oil they would not put some kind of warning on the bottle. Anyway, I will carry on with my test piece and that should at least tell me if the polish is OK or not and if it is, then j guess it must be the oil somehow not being able to penetrate like you say! Thanks again for your input

 

[ED65]

...a technician at fiddes who thought that it's probably the fact that I am using oiI and that Is stopping the shellac from hardening.

:shock: This is just remarkable to me, that he'd think it would be even a possible cause given the wide use of oil in traditional French polishing.

Anyway, it's been two months since you built up the initial layers is that right? Before shellac is too far gone to use it can just takes ages to fully harden, but if it's been months it seems yours is well past the middling phase unfortunately.

 

[Grahamemes]

Hi Ed65, yes it had been about that long. Like Mike said, the melamine could be a factor, but I find it hard to believe that fiddes would not have tested the product with likely scenarios and their tabletop had been on sale for a long time now and they have had no problems like this apparently. I would think if the oil is the problem then someone else would have encountered something similar which is one reason for me posting in this forum. If it is not out of date the only other thing I can think of is maybe I put it on too thick, because maybe it bodies up a bit faster than what I am used to with my own mixed shellac. Again I think this is probably not the case but I am trying to think of all options. My tester piece with no oil should reveal a more solid conclusion In a few weeks. In the meantime I am trying out something on the back of the guitar. I am going to try to draw out any trapped oil by cutting back and wiping with cloth damp in methylated spirits and after I think there's definitely no oil I will re finish with some normal shellac mix. You never know, and I am prepared to strip the guitars and start again but if I can avoid it I will be very happy!
There is also the guitar from before which still doesn't feel right but I was leaving it to see what happens with time, luckily that one was a bit of a test guitar although it would be nice to get it up for sale, the more recent one is for a client who is being very understanding about waiting but It is definitely a pain in the you know what!

 

[ED65]

Hi Ed65, yes it had been about that long. Like Mike said, the melamine could be a factor

FWIW I very much doubt the malamine is a factor myself. The main reason being the most obvious: that aged shellac is known for drying soft without any 'help' from something else

I am going to try to draw out any trapped oil by cutting back and wiping with cloth damp in methylated spirits

I know spiriting off with meths is the traditional way to remove traces of oil but you might like to test out wiping with white spirits, but itself or prior to a very light pass with meths. I've experimented with this a few times recently French polishing small items where you can't easily avoid the arrises (one was an octagonal handle, so lots of them too) and it's been a big help not cutting back too far.

...and after I think there's definitely no oil I will re finish with some normal shellac mix. You never know, and I am prepared to strip the guitars and start again but if I can avoid it I will be very happy!

Fingers crossed!

 

[Grahamemes]

Thanks Ed65, i may give that a try, the one good thing about these kind of things is they can provide opportunities for experimenting as worst case is you may have to start again, which you may have to anyway lol! Thanks for that info and yes I am doubting the melamine too, but hopefully the test piece will confirm that later on!

 

[Grahamemes]

Thought I may as well post a pic of the guitar

 

[MIGNAL]

You should always try to remove any oil used during the F.Polishing process. After a 'session' I let it sit for an hour or so and then gently wipe down with absorbent paper towels. I then take a fresh pad loaded with a touch of shellac/meths and spirit it off. Takes just a few seconds. Leaving the oil on will create a gummy deposit, even with a non drying oil. You see this as witness lines when any cutting back is done. Not too dissimilar to the witness lines you sometimes get with oil varnish. Alternately F. Polish without the use of any oil, it requires a different technique but it's perfectly possible to do.

 

[Grahamemes]

You should always try to remove any oil used during the F.Polishing process. After a 'session' I let it sit for an hour or so and then gently wipe down with absorbent paper towels. I then take a fresh pad loaded with a touch of shellac/meths and spirit it off. Takes just a few seconds. Leaving the oil on will create a gummy deposit, even with a non drying oil. You see this as witness lines when any cutting back is done. Not too dissimilar to the witness lines you sometimes get with oil varnish. Alternately F. Polish without the use of any oil, it requires a different technique but it's perfectly possible to do.

Hi Mignal, thanks for your input.
I would agree with everything say there though I'm not quite sure what you mean by the witness lines. If I'm honest though, I haven't always followed those rules exactly, normally I work till the rubber is dry and then add a few drops of alcohol at the end of my session, kind of like spiriting as I go, often that does leave some oil on the finish, but that seems to rise up to the surface and act as a lubricant for my next session. Sometimes I use paper towels and do extra spiriting if I feel I have used too much oil, and during my final spiriting, I am of course trying to get all of the oil out. Also, during my learning curve (which is still in effect lol!) I often used too much oil and sometimes didn't spirit It off properly, left it for a few days etc, and in the end it never caused any major problems, I am certainly no major expert, but have been polishing my guitars succesfully for five years now and have never had issues with the shellac not going hard, I have always used oil, (I would love to be able to do it without one day though) and this is the first situation like this I have encountered. Have you experienced shellac not going hard, if so, do you think this was because of trapped oil, and was the shellac a straight mix or tabletop etc?
Thanks again

 

[MIGNAL]

The only time I've had issues with shellac is when it is old, either mixed or in the flake. Waxy shellac in it's dry form seems to have an extremely long shelf life, decades. It's the more refined grades that have a relatively short shelf life, although I am referring to years. Once mixed it's usually a matter of a few months, perhaps a little longer for waxy types.
The witness lines that I'm referring to appear as small 'islands' in the finish, kind of like the lines you see on a contour map. It's more common with oil finishes, where a coat does not meld with an underlying coat. When you use an abrasive to flatten the finish you start to see these witness or contour lines ie. the separate coats. That won't happen with shellac, being solvent based the subsequent applications solve the underlying shellac i.e. the finish ends up as one whole layer.
It does happen if you use oil as a lubricant though, either using too much and/or failing to remove enough of the oil. This happens even with non drying oils such as mineral, which seems to gum up and act like a drying oil. Presumably the non drying oil is forming an emulsion like layer. I'm no chemist but there clearly is something that happens that alters it's properties. It doesn't seem to prevent the shellac itself from going hard though, just that it forms a separate layer - which probably is softer than the shellac layer.
The remedy is obvious. Use just enough oil to lubricate the pad, remove the oil after each and every session, don't allow the oil to sit there for long periods of time.
French polishing without oil does require a different technique. You can't work the surface anywhere near as long as you can when using oil. It's more a case of little but often. Use only thin 1 lb cuts, it's much harder with heavier cuts. Change the pad covering frequently. Fresh covering seems to allow the surface to be worked a little longer. You can wash the old used covering in strong bleach solution. I near boil mine in a large pan. The bleach is fairly strong alkaline and alkaline solutions dissolve shellac.
I've not tried the modified shellacs other than the brushing variety.

 

[ED65]

Your guitar looks gorgeous Graham, I do hope you don't have to go back to the beginning!

 

[MIGNAL]

Not sure about the modified shellac but the normal procedure for testing whether shellac is good is to brush a few thin coats on a test piece. Leave it for a couple of days to dry and sand it (dry) with 400G. You should get a white powdery type dust. If the paper starts to clog with tiny gummy deposits there's a good chance that the shellac is having trouble drying. You might want to leave it for a couple of days longer for the modified shellac just in case the stuff takes longer to dry over normal shellac. I wouldn't wait more than 4 or 5 days. A few thin coats should dry in that time, a little different if it was thick multiple coats.
Finish problems can really delay things. Waiting for the original finish to harden and then realising that there is a problem can mean stripping it all off (been there a few times!), reapplying and then allowing the new finish to thoroughly harden. On a guitar I wouldn't hand it over until the shellac has hardened for at least 3 weeks.

 

[Grahamemes]

The only time I've had issues with shellac is when it is old, either mixed or in the flake. Waxy shellac in it's dry form seems to have an extremely long shelf life, decades. It's the more refined grades that have a relatively short shelf life, although I am referring to years. Once mixed it's usually a matter of a few months, perhaps a little longer for waxy types.
The witness lines that I'm referring to appear as small 'islands' in the finish, kind of like the lines you see on a contour map. It's more common with oil finishes, where a coat does not meld with an underlying coat. When you use an abrasive to flatten the finish you start to see these witness or contour lines ie. the separate coats. That won't happen with shellac, being solvent based the subsequent applications solve the underlying shellac i.e. the finish ends up as one whole layer.
It does happen if you use oil as a lubricant though, either using too much and/or failing to remove enough of the oil. This happens even with non drying oils such as mineral, which seems to gum up and act like a drying oil. Presumably the non drying oil is forming an emulsion like layer. I'm no chemist but there clearly is something that happens that alters it's properties. It doesn't seem to prevent the shellac itself from going hard though, just that it forms a separate layer - which probably is softer than the shellac layer.
The remedy is obvious. Use just enough oil to lubricate the pad, remove the oil after each and every session, don't allow the oil to sit there for long periods of time.
French polishing without oil does require a different technique. You can't work the surface anywhere near as long as you can when using oil. It's more a case of little but often. Use only thin 1 lb cuts, it's much harder with heavier cuts. Change the pad covering frequently. Fresh covering seems to allow the surface to be worked a little longer. You can wash the old used covering in strong bleach solution. I near boil mine in a large pan. The bleach is fairly strong alkaline and alkaline solutions dissolve shellac.
I've not tried the modified shellacs other than the brushing variety.

Thanks for that info, with regards to the shelf life, that is my line of thought too, I have only once had an issue with the flakes and that was a blonde (bleached) flake and when I mixed it it still had not dissolved properly after a week and was a bit jelly like, at first I didn't think the flakes had shelf life and although there are reports of people using extremely old blonde dewaxed flakesI, It seemed as though this was the case so I didn't use it but think i strained it and maybe used it as a sealer.

Thanks for explaining the witness lines, I don't think I have 'witnessed' (pardon the pun) that yet with my polishing but it makes a lot of sense, there are definitely chemical reactions taking place during the process so it's good to be aware of those to help deal with any issues that may arise.

Finally, If you don't mind Sharing some of your technique, i am interested, do you use the same cut all the way to the end or do you thin it out as you get towards the end? Do you cut back at all at any stage and/or do you use pumice to help flatten throughout, like I said I would like to polish without oil and will probably keep trying to do so as I don't use any oil in the early stages anyway, so I may as well try and worst case, I have to cut back a little and maybe finish with a bit of oil if it's still not feeling it without!
Thanks again, and no problem if you don't want to share that, I know how tricky it is trying to explain polishing technique as it's something you have to learn by experience really!

 

[Grahamemes]

Your guitar looks gorgeous Graham, I do hope you don't have to go back to the beginning!

Thanks, apreciate it, I hope so too, but I guess it's all part of the experience and you just have to roll with it!

 

[Grahamemes]

Not sure about the modified shellac but the normal procedure for testing whether shellac is good is to brush a few thin coats on a test piece. Leave it for a couple of days to dry and sand it (dry) with 400G. You should get a white powdery type dust. If the paper starts to clog with tiny gummy deposits there's a good chance that the shellac is having trouble drying. You might want to leave it for a couple of days longer for the modified shellac just in case the stuff takes longer to dry over normal shellac. I wouldn't wait more than 4 or 5 days. A few thin coats should dry in that time, a little different if it was thick multiple coats.
Finish problems can really delay things. Waiting for the original finish to harden and then realising that there is a problem can mean stripping it all off (been there a few times!), reapplying and then allowing the new finish to thoroughly harden. On a guitar I wouldn't hand it over until the shellac has hardened for at least 3 weeks.

Sounds about right, and a good way to test it if you are unsure, come to think of it, I have noticed that my sanding pads have been gumming up a bit more than normal, I just put it down to maybe the tabletop or the oil, but when I used to use my own mix the pads never gummed up that bad hmmmm,

Thanks again, gonna run some more tests now
I really appreciate your input, it's definitely helping me clarify what may be the causes!

 

[MIGNAL]

I'll give a quick explanation of the technique that I use.
I apply some sort of drying oil first, usually something like Tru oil. If the wood has open pores I'll fill it with the Tru Oil and pumice or use the oil sand fill. I won't start applying shellac until that has thoroughly dried and hardened. Sometimes it takes two applications to fill the pores. I also try to remove as much of this from the surface i.e. in the pores rather than sitting on top of the wood. I do want the oil to pop the grain of the wood, so if I cut through in any area it does mean that I will have to wipe that area with more oil, otherwise it will start to look patchy when applying the shellac.
I use a 1 lb cut, all the way through right up until the 'glazing' stage, where I switch to something a little less than a 1/2 lb cut.
I do little cutting back between sessions, only when it is necessary and with 800G used wet. There really shouldn't be any need to use a coarser grit (unless things are really uneven) and why remove shellac that you've just put on?
Once I think that the finish has built up sufficiently I let the surface harden for a week or so. I then cut back wet with 1,000G, using random circular patterns. Of course that leaves scratches. This is where I differ from a lot of 'modern' French polishing. It seems as though many now go through all the grits, then to fine polishing compounds and even buffers. I'm not that fond of the resultant glass or plastic looking wood that this gives, it's too extreme for my tastes. Others have a different attitude to this. Instead I switch to the 1/2 lb cut and use the pad in slightly overlapping very straight lines, going with the grain. It takes a minute or less on the back of a guitar. Then I let it dry for a couple of hours. I continue to do this cycle until all the scratches are filled in, so multiple times at these very mini sessions. May seem fussy but very little actual time is spent on each surface. Eventually I'm left with a glossy surface but with very fine micro lines (NOT scratches) left from the cloth, just enough to take the hard glassy edge off. You might call it more of an organic look although you shouldn't see any whip marks, just very straight micro lines. I'm perfectly happy with that type of effect.