Shellac problem

[IanW]

I've struck a bizarre problem trying to French polish a box lid. It's a piece of spectacular spalted & blue-stained mango wood, which I have polished successfully before (though obviously not this particular piece). I'm using Ubeaut premixed white shellac which is near the end of its use-by date, but it is doing fine on the Qld maple sides of the box, so I doubt aged polish is the problem, though it may be a contributing factor.

When I started "bodying up" the fresh wood things appeared to be going normally, but as I proceeded with subsequent applications, a couple of bare patches began to appear at each end of the raised panel, and just kept growing on each rub-over. Half of the surface is building normally, it's just these two patches near the edges that aren't cooperating. There seems to be polish in the surface of the wood, but further coats just don't want to adhere to it. The mango was given to me years ago & I don't know its full prior history, but as far as I know it was never treated with any chemicals and I certainly haven't done anything to it. It has been well-stored in a dry area for the last 10 years at least.

I've been polishing for 60 years and not encountered a similar problem before so any suggestions as to what's going on & better still, how to get around the problem would be greatly appreciated, otherwise I'm going to have to rip it off & try some other finish....

Cheers,

[Mobyturns]

I have no answer on the shellac issues. Pretty tough when shellac won't stick!

However, I have encountered a similar problem with applying CA finish to pen blanks at the Prossy Turnout a few years back. I had prepared a number of turned and fully sanded inlay segmented pen bodies ready to have the CA finish applied. The CA went on all of them with no apparent issues however a number in the batch later failed in large patches as I wet sanded the finish. The patches were remarkably about the size of finger and thumb prints.

The failures were on more than one species of wood with other blanks of the same species unaffected.

The only explanation I have come up with is that "someone" had handled them with some sort of "contaminant" on their fingers whilst we were at smoko. Most likely it was a wax, PTFE or silicone based spray.

[mic-d]

High porosity due to spalting in those areas? I have some blonde dewaxed made up you can try if you like...

[IanW]

>Pretty tough when shellac won't stick!<

Indeed, MT, shellac is often the go-to to cover problem surfaces when other finishes aren't taking!

High porosity due to spalting in those areas? I have some blonde dewaxed made up you can try if you like...

Michael, that is what I first thought, the blue-stained areas are certainly more porous, but there is blue-staining in plenty of areas where the shellac has taken ok. I should have posted a picture this morning, but hadn't taken one, so here is a pic. The arrows point to the middle of the areas that aren't holding the polish (they look shiny, but they aren't in reality): Picture1.jpg

I'm beginning to think it is the polish & not the wood, I rubbed some onto a bit of fresh wood & it remained sticky for much longer than it should, so it may be that I keep rubbing the polish off as I try to apply more (though why it's still building elsewhere is a puzzle). I checked the use-by date again & it's actually a couple of months over, so that's not a good start, my shed isn't the ideal storage place for finishes like prepared shellac.

So I might pop over in the next day or two and try some of your brew & see what happens...
Cheers,
Ian

[IanW]

I'm pleased to report that with Michael's help, my problem has been solved. It was indeed due to the shellac having 'gone off' & not drying properly. Even after leaving it a whole day to dry, it still had a slightly sticky feel and when I rubbed on a fresh coat, it softened the previous coat almost immediately & prevented any build up unless I applied way too much, which left a very poor surface. The fresher shellac behaved as I expected and was touch dry within seconds of application. So I've scraped the old stuff off & started afresh - it's already looking way better after a couple of quick goes with a nearly empty rubber.

I can't explain why the problem manifested far more on the mango lid than on the Qld. Maple sides, and even on the mango it was building in patches, but I'm in no doubt now that my shellac is the culprit. Lesson learnt, I've not pushed shellac past its use-by date before, and I certainly won't do it again!

Cheers,

[The Spin Doctor]

Old shellac is a bitch. Ya only know when it's no good, after you've committed. Just gone through that. Sand it all off, and start again.

Probably a combination of short grain and old shellac. Short or end grain is going to pull the alcohol in and releases it more slowly. Which means the shellac is softer in those areas.

[IanW]

... Probably a combination of short grain and old shellac. Short or end grain is going to pull the alcohol in and releases it more slowly. Which means the shellac is softer in those areas....

Actually, purely an "old shellac" problem as it turns out, SD. What was confusing me at first is that there wasn't anything different about the bare areas compared to areas that seemed to be holding polish. True, the areas that weren't cooperating were affected by the spalting & bluestain & were a bit porous, but similar areas were coming up ok, or seemed to be, I realised when I started using some of Michael's brew that it hadn't been building properly either, due to the retarded drying. In retrospect, I think I know exactly what happened - the two spots where it all began were a bit light-on after initial bodying-up, so I gave them more attention as I started trying to develop a polish. Because the shellac wasn't hardening normally, the early coats were easily dragged off & the more I tried to compensate by going over then a bit extra each time, the worse it got.

Anyway, I have had the lesson not to use out of date or nearly out of date mix thoroughly driven home. The reason it has taken me 50 plus years to learn it is because up until a few years ago I always mixed my own brew from flakes, it has only been the last few years that I have taken to using pre-mix to save time & bother (or so I thought). I just bought some fresh flakes & will be reverting to my old practice of just mixing what I need when I need it...

Fortunately, all is now well. I scraped most of the gluggy stuff off and the fresh polish seemed to set the residue off, after an initial coat, it dried quickly & I could proceed with the job as I normally would. The result is acceptable:
Lid.jpg

aAd the recipient (daughter) seems delighted with her xmas present, a somewhat OTT set of tree ornaments:

Contents.jpg E set.jpg


Cheers,

[rustynail]

Ian, It will be interesting to see if, in time, the finish starts to break down. This has been my experience with polishing over sticky, out of date shellac. As apprentices we were told to always remove or "kill" the faulty stuff before proceeding with a fresh batch of schellac.
I always mix my own from flakes for the very reasons you have pointed out.

[IanW]

Ian, It will be interesting to see if, in time, the finish starts to break down. This has been my experience with polishing over sticky, out of date shellac. As apprentices we were told to always remove or "kill" the faulty stuff before proceeding with a fresh batch of schellac.
I always mix my own from flakes for the very reasons you have pointed out.

That possibility was certainly at the back of my mind, we were told much the same thing by our school woodwork teacher (an ex cabinetmaker) when he taught us French polishing. He was old-school & insisted we do things 'properly'.

I scraped the lid back to bare wood, mostly - couldn't get the edges of the fielding as clean but the new polish went on easily, with no hint of delayed drying and the subsequent build & polishing seemed normal, so I hope that part will be ok. However, due to laziness & lack of time I just rubbed the sides over as well as I could with steel wool which meant there was still a fair amount of polish in the pores (they're Qld. maple). The problem with not drying wasn't so obvious on the sides, I hadn't touched them for a couple of weeks and there was no tackiness on them at all, like there had been on the lid.

So I'll cross some fingers & hope it doesn't crack up too quickly. I know the customer won't hesitate to let me know & demand it be fixed if it does,,,,,

Cheers,
Ian

[ubeaut]

Sorry for the late reply Ian.

When white shellac hits it's best before date, it's expired and definitely not best after that date. However what you have left can be mixed with 100% or at least 95% ethanol (metho) 8-10 parts metho to 1 part white shellac and it will work as a grain raising sanding sealer for many years to come.

For what it's worth... Mango has been a problem with White Shellac before. Not all Mango but some and with a similar patchy sections as per your top. Usually on the more open graine mango and often after the first few coats due to either burn in from too much shellac in rubber or missed sections having a coat or two less then trying to catch-up, you end up with brighter shine on the rest and slightly duller in the missed bits that haven't been able to catch up.

Often happens if user has sanded a section with a problem then tried to recoat said section to blend in with the rest.

Sanded section has 1 coat the rest 4 or 5, go over the entire surface again and sanded has 2 coats the rest 5 or 6, it's very hard to play catch-up. You either have to be brilliant polisher or sand the entire surface back and even a brilliant polisher will just sand the whole surface back, clean it off with a metho wash and start from scratch. Takes a little unnecessary time but will give the best results and save a bit of frustration and gnashing of teeth later on.

We label our white and Hard Shellac with 18 month best before date because we use a heavier mix of shellac to ethanol and only ever use 100% Industrial Ethanol (100% IMS), most mixed shellac is best used within 6 mth. Even your own mix.

The White should be used or put down so Sanding Sealer before Best Before date, However our Hard Shellac has been reported as being as good up to 8 years after B/Before date. Working perfectly, drying as it should and hard as a rock when fully cured. I have no idea why this is the case but put it down to the hardener we use. The surface shines like a great French polish but has the hardness of a melamine bench top.

We have a couple of furniture companies that regularly get 25 lt drums from us. one has been using it for around 25 years for restaurant and café' tables, etc and says that some of the 25 year old finishes are as good today as when they were first done. That's almost unheard of with polyurethane, and many lacquers.

Hope this is of some help/interest.

Cheers - Neil

[IanW]

Thanks Neil, much appreciate the detailed reply, it is helpfu, and a good caution to others!

This bit certainly strikes a chord with me: <....it's very hard to play catch-up. You either have to be a brilliant polisher or sand the entire surface back and even a brilliant polisher will just sand the whole surface back, clean it off with a metho wash and start from scratch. Takes a little unnecessary time but will give the best results and save a bit of frustration and gnashing of teeth later on.....>

I decided a very long time ago that when things go pear-shaped on a polish job, it's best to start over, the time it may take to remove the mess is nothing compared with the time wasted in trying to 'fix' it - my experience is it always goes from bad to worse. Sanding off even cured shellac is an exercise in frustration for me, the paper clogs instantly & irretrievably, especially if the polish is not hardening properly. A well-sharpened scraper is my best friend in such situations. If I really want to get back to 'clean' wood, I use some metho-soaked OOOO steel wool, but that has to be done cautiously, if the wood you are working on contains any tannins, there's likely to be enough water even in fresh metho (as you mention somewhere in your literature), to cause some nasty staining - damhik! I know lots of people prefer using plastic scouring pads, both for that reason & because they don't leave tiny bits of steel in the work, but they just don't work as well as steel wool for me, for whatever reasons. As long as I clean up meticulously it's usually ok...

I've tried to patch a few French-polished pieces and I dips me lid to people who can do that flawlessly! Even when I blend the patch perfectly with the surface, the patch remains glaringly obvious because it's new, the shellac itself is a different colour/intensity and any fillers that were used are near-impossible to match (by me). If it's a valuable old piece, I won't touch it, & if it's one of my own, Ive found the easiest way is to smooth & blend the old finish with metho-soaked steel wool and re-polish from there - done with a little care it re-finishes very quickly & easily. Not sure that will work with hard shellac? Dunno, I haven't yet had to fix anything where I've used hard shellac, but I presume it will only come off with sanding or scraping? With luck, I may never need to know the answer to that one....

Oh yeah, one other important thing about polishing I've discovered is to choose your weather! On warm, dry days, things can go swimmingly, but in cool, damp weather such as we are experiencing right now, it can be painfully slow. August - September is the best time of year for polishing in S.E. Qld, I reckon - I don't know how professional polishers made a living the rest of the year.....

Cheers,
Ian

[Mobyturns]

We have a couple of furniture companies that regularly get 25 lt drums from us. one has been using it for around 25 years for restaurant and café' tables, etc and says that some of the 25 year old finishes are as good today as when they were first done. That's almost unheard of with polyurethane, and many lacquers.

Hope this is of some help/interest.

Cheers - Neil

You have sold me the farm - .

Must get some and some Aussie oil to try.

Very interesting your comments about finishing mango. I have experienced similar issues with some mango specimens. My thoughts are that it is most likely caused by the way mango degrades then spalts, and is related to the fungi in the wood in the "punky" areas.

[ubeaut]

Ive found the easiest way is to smooth & blend the old finish with metho-soaked steel wool and re-polish from there - done with a little care it re-finishes very quickly & easily. Not sure that will work with hard shellac? Dunno, I haven't yet had to fix anything where I've used hard shellac, but I presume it will only come off with sanding or scraping? With luck, I may never need to know the answer to that one....

Huh, neither do I. To date I've never had to do it and have never heard from anyone who has so maybe it's just that good that it never needs repair work done on it. Initially we used to recommend putting an initial coat of the dewaxed white shellac down as a base to make it easier to strip. But it's so damn tough that the stripper doesn't seem to want to touch it.
Who'd a thunk it?

Very interesting your comments about finishing mango. I have experienced similar issues with some mango specimens. My thoughts are that it is most likely caused by the way mango degrades then spalts, and is related to the fungi in the wood in the "punky" areas.

Yeah I hear what you're saying. Definitely not my favourite wood at least what I've had wasn't. Punky open grained and not really pretty, bordering on greyish green. Urk... Not anywhere near as nice looking as the piece on Ians' box.

[IanW]

...... Not anywhere near as nice looking as the piece on Ians' box. :2tsup...:

And I've still got a little bit left.....

I can see how mango could drive you nuts, though, it's a fairly coarse-grained wood, and takes a lot of work to get it smooth without filler, which I didn't want to use because I thought it would muddy the patterns, especially the fine, sharp spalt lines, & I already knew from oiling & varnishing other bits that the blue-stained areas are more porous and would respond differently. So I just worked as much polish as I could into any areas that slurped it up quicker than the other areas - it can take a bit lot longer than using a filler, but eventually I get where I want to be...

Mango is a probably not a great choice for french polishing, I agree, it's certainly not as good to polish as woods like red cedar or Qld maple, which are equally coarse-grained, but polish easily (something I have never managed to figure out!). It's probably better to apply an oil or some non-shiny finish & not try to make it super flash. I applied Scandinavian oil the first time I used some of the spalted stuff, which was for door panels on my tool cupboard: Toolbox front red.jpg

Apologies for the very amateurish photography, but it shows what I want to demonstrate, which is the matte finish on the mango panels and the more glossy surface on the N.G. rosewood door frame after the same number of coats. It is a bit OTT for a tool cupboard, but it does get people's attention...

Cheers,
Ian

[Mobyturns]

I believe mango gets a bad wrap mostly because the mango wood most wood workers get to use is from suburban back yard trees that have been well watered and fast growing - and is typically hosting hidden "treasures" like nails, wire, bolts, star pickets, galv fence posts, bottles, rocks, horse shoes, - you name it.

Wood from trees that have had a tough life seems to be much better. I have found Red Cedar, most of the "silky oaks", Tamarind, & Black Bean wood to be the same, well almost all woods that come from suburban environs. One exception seems to be African Mahogany which seems to produce quite consistent quality wood no matter the source from my limited experience.