shellac problem ?

morn'n all ...


seem to have a problem when i get to the second coat of shellac, i brush it on and it seems to react with the previous coat:((...disolving it in a not so good way, it kind of goes a little bubbly and very cold and moist...

this problem happens reglardless of weather or temp, and i even leave the job 24hrs between coats, i know i use metho from bunnings but i have always used this stuff and when i first started using shellac this way a couple of yrs ago , i never had a problem, i then got into oil/varnishes instead but have wanted to return to a shellac finish as the bulk and the floorseal as a final coat only...

anyone know of the problem or had the same experience ?

Hi La Hureta,

hmmm, could it be a bad batch of metho or the shellac has turned?

Testing the metho - UBeaut posted something here about testing the metho - don't quote me but I think it was adding something to a sample of the metho, mixing it and seeing how cloudy the metho became. I believe it was in one of the shellac - where do you get your metho from type threads here in Finishing.

As for the shellac, how old is it?

Is it the ambient temperature, or even this particular piece of timber, or even the brush?:?

cheers
Wendy

shellac is new, metho is from the hardware, yes i know it's not 100%, but i never had the problem before, brush does'nt matter, same relults, i still use shellac for a sealer and so i buy a lot of it often, so it's always fresh (i get 1kg tub of flakes at a time)

Quote:

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Originally Posted by la Huerta

morn'n all ...

seem to have a problem when i get to the second coat of shellac, i brush it on and it seems to react with the previous coat:((...disolving it in a not so good way, it kind of goes a little bubbly and very cold and moist.

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The only reason I can think of for this happening is the first coat is not dry completely, maybe you should try putting more meths in the first coat to hasten the drying and less meths in the second coat so it doesn't dissolve the first coat.

Quote:

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Originally Posted by la Huerta

this problem happens reglardless of weather or temp, and i even leave the job 24hrs between coats,

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Is it possible for you to experiment on a small workpiece indoors where you could keep it at a constant room temp just in case it is the ambient atmosphere in your work area that is causing the problem. Weather conditions have been a bit strange lately.

Seems strange you have not had this problem before. I know you said you buy in fresh materials but maybe the supplier you are using has a bad batch of Shellac or meths. Start from scratch and buy from another supplier, see if you get the same problem.

Another problem you may be having is that the first coat has, for some reason been applied too thickly.

Shellac is my finish of choice but in present WIP I used super blond shellac for the first time and added a red dye. Shellac was fresh, meth was fresh but the mix took ages to dissolve and when I painted it on ( not my normal method of application) I found it remained tacky. Next day I applied straight meth with a rubber and it solved the problem.

I would not suggest application of any more shellac meth mix at present because more mix, however diluted just adds shellac and thickens the coating.

The meth pullover method is one I've used in the past with problem shellac finish. My wife was over enthusiastic in applying shellac to the interior of our yacht and next day we found it had crocodiled. Pullover with the meth rubber solved that problem too..

Including photo of WIP to help you see that, unlike some other finishes all is not lost with shellac problems and the meth pullover works well

Things Id check:

1. Humidity. I have a heater and dehumidifier running in my workshop when I French Polish.
2. Water content of the meths. I use technical grade meths for my french polishing. I generally dont buy much from Bunnings...others in here will disagree with me but generally quality of their stuff is not that good and I believe in the old saying "you get what you pay for".
3. Jerryc may have a point regarding amount of shellac youre brushing on for each coat. Try brushing on less shellac and see if that makes a difference.

Cheers Martin

Quote:

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Originally Posted by jerryc

I found it remained tacky. Next day I applied straight meth with a rubber and it solved the problem

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This might be your first thing to try if you continue to have the problem.
Maybe you are putting it on too thick thats why I suggested diluting your first coat more than usual but thats if you are starting from scratch with a new piece of timber. As jerryc said don't apply any more shellac to the piece you already have problems with.
By applying the first coat too thick you could be creating the problem yourself and its not drying in the current climate conditions.
Let us know how you get on. Good luck.

la Huerta - Where are you getting your flakes from? It is possible they have been there for a really long time. Best to buy from someone you know has a large turnover or who specializes in shellac.

To test metho for water content take out a little of the meths from the bottle and add a good dollop of mineral turps then shake (the bottle not you). If it stays crystal clear it is fine for shellac, if it goes cloudy (even a little) it contains more than a little water and really isn't suitable for shellac, if it goes milky it has way too much water and is probably only good for cleaning windows.

Think you'll find more and more metho is being watered down for profit I have seen some that had round about 43percent water content which meant it was barely Over Proof (OP) i.e.: able to burn. Just because the label says 95% doesn't mean it only contains around 5% water. Think you'll find it could contain up to 20% water and legally be called 95% (supposedly not done by the top brands). If it's not marked 100%IMS or 95% or Industrial Methylated Spirits, the chances are it really won't be suitable for use with shellac.

What mixture of shellac to meths are you using?

Does the shellac pretty much completely dissolve within an hour except for a few ratty bits on the bottom?

Do you strain the shellac through a filter after mixing eg a few layers of muslin or some voil or chiffon material etc?

Are you brushing the shellac on like paint?

What kind of brush are you using?

How fine are you sanding the timber before applying shellac?

Did you seal the timber with an extremely weak coat of shellac (1 part to 10 parts metho) after sanding and before first coat of polish?

There are just some of the many variables that could be affecting the finish. Supply a few answers and I may be able to help.

Cheers - Neil :)

Neil This matter of meth quality is certainly an eye opener to me and I thank you for the clarification.

As I said in my post above, I had trouble with blond shellac not dissolving quickly. Question. The blond shellac, purchased from a well known source in WA, when opened was often clumped and many of the clumps could not be broken by hand. Would this be normal ?-- Could it have been old stock?I never had this happen with ordinary orange shellac. I put down the slow dissolving rate to it being blond and to the addition of the dye. Was this so?

Never too old to learn

jerryc

G'day Jerryc - Clumped Shellac usually means it has been subjected to heat, in this case most likely a hot summer. Blond shellac like most is best stored at around 4 degrees C.

However most shellacs will also clump a bit under pressure and as it comes in 25kg bags in a sea container all the way from India it can be subjected to some extremes of weather as well as many tons of weight. So you would expect that some of the bags on the outside of the pack might be effected by heat and pressure and tend to clump slightly. Unless of course it comes into the country in a Refrigerated Container (as ours does) and is handled correctly once it arrived.

I saw many thousands of dollars worth of white shellac ruined, because it was left on the wharf in in Melb indirect sun for a few days, in the middle of summer. 10 tonne of 25 kg shellac bricks. Usually crushing will fix the problem.

Sorry, I digressed. Blond takes a lot longer to put down into liquid than regular shellac which should be pretty well dissolved within an hour of hitting the meths. Blond can take several hours under constant agitation and if it has clumps that haven't been broken up it could take a day or so even with the best alcohol.

I have never added dye to blond shellac so I am not sure if this would have caused or added to your problem. The most wonderful thing about shellac is the fact that it is easily repaired if something does go wrong.

I have a 25 kg bag of Blond which I will be putting down to liquid today so I will let you know how long it takes, it has no clumps in it as it has been in cold storage since it left India and is definitely in cold storage here as it is freezing at the moment. Is will be mixed down with 100% IMS this is 99.5% pure ethanol with 0.5% denaturant.

We usually leave our white shellac stirring for 12 hours to dissolve it so it will be interesting to see the difference with the blond. This is the first time I have mixed a big lot, as up until now we have never use it in production.

Cheers - Neil :U

Hi Neil,
was hoping you would come to the rescue here, thanks. The tip on how to determine too much water content in meths is great. I never knew that so thanks for that too.
So, for the record, Neil, what is the best method to use for storing shellac and how long can it keep so as to be okay to use. What should we look for when buying shellac to check if its fresh enough to use.
Just as a point of interest, I remember my dad putting a bottle of meths in the petrol tank of his car, said it absorbed any water in the petrol and made the car perform better. He use to do this about once every couple of months, didn't seem to do any harm and the car did seem to perform okay. Is this just a myth or does it really work?:rolleyes:

So, for the record, Neil, what is the best method to use for storing shellac and how long can it keep so as to be okay to use. Shellac flakes are best kept in a cool dark place. Can be kept for a long time in the fridge. This is the best way to store almost all shellac. Do not store in tin as it will react badly with the shellac and turn it black.

What should we look for when buying shellac to check if its fresh enough to use. Pretty hard to tell if it's fresh or 10 years old. Usually if it's solid or clumpy it is in poor condition and should be avoided. If it's bright in colour and the flakes move freely in the bag and clumps can be broken up easily by hand then it is probably in good nick and pretty fresh.

Best to buy all of the flake shellac in the flake form as they have a pretty good shelf life onless subjected to direct sunlight and heat i.e.: orange, blond, super blond, astra, ruby, brown, etc. The white shellac or Dewaxed White are best purchased in liquid form as they have a much shorter shelf life in the raw form. If mixed with 100%IMS as ours are they have around 2 years usable shelf life as a finish and can then be cut with metho and used as sanding sealer with an indefinite shelf life.

Just as a point of interest, I remember my dad putting a bottle of meths in the petrol tank of his car, said it absorbed any water in the petrol and made the car perform better.
He was right it does dewater petrol and it works well. Don't know about the running better bit in modern cars. But in the older cars almost anything that would burn would make the motors run better, ether was often used to bump up the octane level and give a bit more speed. Heard of one old boy who used to put moth balls in the petrol.

Ethanol (metho) is what they are putting into the fuel now and many makers are saying it isn't good for motors as they will burn out much sooner, unless they are specifficaly designed to run with ethanol in the mix.
He use to do this about once every couple of months, didn't seem to do any harm and the car did seem to perform okay. Is this just a myth or does it really work? I wouldn't be doing it in any modern engine.

Cheers - Neil :)

Thanks for that Neil

hey guys...

sorry i have not responded to my own thread, i kind of forgot about it:-
hav'nt done any finishing for a while because of the cold damp weather, but back into it now...

thanks Neil and everyone else for the great tips, (there is so many of them !:U) ,

yes...i think one of the problems is, i was laying the first coats on to thick, i see now how it's better to start of thin

jerryc , how many coats of that red tinted shellac did you do to get the color, i mean did you tint the shellac lightly and build it up , or a heavy tint and fewer coats, and what cut...

la H:2tsup: