shellac drying times

[la Huerta]

hi all fellow woodworkers...


how long should shellac really be left to dry before poly or lacquer is applied...

had the odd bad experience with the poly disolving the shelac and stain under that, even though i'd allowed 24 hrs drying , perhaps there was not enough shellac to properly seal the stain???...perhaps it was still not 'set' hard

anyone had his sort of delema...

[Auld Bassoon]

Hi La Huerta,

I'm not sure why you would want to apply poly-U or lacquer over shellac; I just use wax over it, else poly without shellac...

[durwood]

I'm with Steve why are you using shellac you need a good reason to use it?
Shellac can be used as a sealer but its usually the last resort for a painter. Because it only dissolves in metholated spirits and drys quickly shellac is good to seal off timber that tends to soak up paint. (end grain etc) as only metholated spirits dissolves it, it won't move when other finishes are placed over it. If a paint finish was under the shellac it would stop the new one attacking it as the new finishes' solvent could not soften the shellac.

BUT!!! it can be problem as it is weak stuff and doesn't like hot, doesn't even like warm. Ever noticed grandmother always had glass on the dining room table or alway put down coasters and place mats before putting the meal out. a hot cup of tea will mark a shellac coating. If you leave a shellac finish in the sun it will blister real quick especially this time of the year.

If your finish is dissolving it, there is metho in the solvent of the paint finish you are using, normally its only in cheap finishes as its a cheap way to pad out the amount of product being sold.

So only use it if the surface is indoors and not likely to be subject to any heat, so its OK on the house fittings- walls, doors - general furniture, chairs, wardrobes but not tables and the like.

If you are using a poly or varnish finish to get a good tough surface and its not a real soft blotting paper type timber skip the shellac. Put a thin coat of poly and let it soak in and dry give it a light sand and then follow up with the finish as recommended. Always brush the first coat of anything, Paint, oil etc especially if you are going to spray the final coats,

If you spray first up air gets to the timber before the paint and fills up the paws of the timber and you risk getting air bubbles under the finish, brushing stuff the coating into the grain.

If you are ever using lacquer there is a lacquer sanding sealer for it, its made to eliminate the need for shellac.

hope that helps you.

[la Huerta]

i use black japan which requires a few coats of shellac to seal it so it does'nt 'bleed' into the topcoat...this whole process is a pain in the neck but i am yet to find anything that will replace the look i get using the black japan...i use old oregon which has the same sort of problems like pine does , with the funny grain, thined BJ is able to flood the surface to give an even result, a dark iridescent walnut colour like the table (not chairs) in the pic (not my table by the way), if someone knows of another way to get this colour...do share your thoughts...

[Auld Bassoon]

La Huerta,

I'd have a look at Neil's book, and the Ubeaut website (http://www.ubeaut.com.au/ubhome.htm) and use white de-waxed shellac first, then hard shellac over the BJ. You are quite right that BJ can bleed through other finishes (been there ), but with regular then hard shellac you should be ok.

As well, whilst dampness and heat is an issue with regular shellac, uBeaut's hard shellac dispenses with that problem .

Give it a whirl on some scrap, and you'll see what I mean.

Cheers!

[la Huerta]

so are you saying to seal with white de-waxed , then BJ, then hard shellac...


if it's a dining table then it's got to be tough too, hence the use of varnish or lacquer

[JB]

Use 2 different sorts of shellac??! Give me a break...

Mate, at this time of year in Australia shellac will be dry in half an hour. Here in Brisbane it's dry in about two minutes. We are after all talking about the time it takes for metho to evaporate...

If your black Japan or whatever is dissoving after one day then it will dissolve after one year. I'd suggest either another thin coat of shellac, or apply your first coat(s) of lacquer/poly thin so they don't sit long enough to dissolve the shellac/japan.

[la Huerta]

thanks JB, this is what i'v been working on, and i buy the shellac in bulk flakes so it's dirt cheap...am going to try out a good quality waterbased finish,that should take care of the disolving issue, all i want to do is put on a barrier to protect my work from the everyday life, if waterbased floor finish does it's job on floors then it should work just fine, it'll be bees waxed after that to give the piece back it's lustre...

how does this all sound...

la H

ps...love your dog JB

[JB]

Sounds ok, though some experts might question applying water based finish over shellac. Whay noit skip the shellac altogether?

Rusty says g'day

[la Huerta]

yeh i may try that, but it will only be a couple of wipe coats of shellac anyway...i just got some cabots crystal clear and wiped it on thinly instead of brushing, so far so good, a couple of thin coats should seal it all ok, then i'll wax as normal...brush on lacquer was aslo something i'd like to try but can't find anyone stocking it...

[la Huerta]

funny , i remember back in the school days and i'm sure the teacher gave us brush on lacquer to use...any woodworking teachers out there...






la H


hey it's my 400th post !!! look out ozwinner i'm catching up (should only take 100yrs or so)

[echnidna]

Love the color of your table.
Some of that rich color is undoubtedly due to the shellac.

I used to use shellac as a sealer over stains that are incompatible with lacquer. I used to let the shellac cure overnight.

If you want a jet black stain try india ink.

[durwood]

There is two different things happening in this thread,
In one the shellac is being put on first then a coating over it and in the other the shellac is being put on over the top of a finish. (black Japan in this case.

If a new coat attacks the previous applied one it usually means the solvent had attacked the coating.

Black Japan is thinned with turps and the shellac is thinned with metho so it has no affect on it. But oil based products like Black Japan and enamel don't dry by evaporation they dry by oxidation which means they dry by mixing with the oxygen in the air.

Thats why you get a skin on the top of the paint when its lid is put back on. the air inside sets the surface of the paint in the tin. It won't re dissolve in solvent once this happens so when a strong solvent is put on it it act like paint stripper and the paint disintergrates. The metho does not do this, its not strong enough it just forms a coating on top.

If you use any turps based finish over the black Japan it should go on Ok as the paint won't be attacked by the turps otherwise you would never be able to put on more than one coat.

Black Japan used to be the base for a lot of black paint work 80 years ago around door frames and on timber in houses and on furnature. You often see it usually under old chairs tables and desks which then copped a coat of white or coloured enamel 30 years later.

If I brought Black Japan today I would suspect it was the base black varnish used in those days. It always needed additives to be applied to it before it could be used easily and dryed fast. The main one being a paint drier called "terebine"

When doctored properly Black Japan dries real fast - so much so its the reason Henry Ford used it to paint his cars black, a Model T needed to be dry in minutes because of the number being made on the assembly line. And believe me it drys like a rock and nothing will soften itif its left to dry completely.

Echidna!
India ink may be worth a shot but from memory its not neally as black an JB it has a blue /green tone when thinned down.

[Auld Bassoon]

uBeaut's dyes or even (dare I say it?) Watson's Proof Tints can give a nice solid black which can be covered with something like FloorSeal (satin or gloss) if one needs a nice smooth black (or green , blue, red). I can understand black, but some of the other colours, well?

BTW: Heads up folks! Has anyone here tried to dye/colour poly-u or products like floorseal? If so, with what?

Cheers!

[la Huerta]

durwood...that is by far the most in depth piece of info i have ever read on BJ, and i'v searched every corner of the web...one of the problems i may be having is it not drying properly, therefore it's still at the disolving stage, it's interesting about the terebine and the fact that the old stuff used to dry fast, i'll have to get my hands on some...

did some expementing today and used the BJ a little thiner and it did dry faster. the waterbased varnish looks ok(maybe just a tad plastic looking),but of cause created no problems, although i'm still a huge fan of the shellac finish so one thing i'm still interested in is the hard shellac, does it have the same durability as a varnish or lacquer...

hope others are benifiting from my ambition to get this right.