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Tide marks on shellac finish

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cookiemonster

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Hi everyone.

I'm trying to finish a teak coffee table with Boiled Linseed Oil followed by a shellac top coat.

The oil is easy but I'm having trouble with the shellac.

I'm using a homemade concoction of dewaxed blonde shellac flakes + meths , applied by paint brush, with a light rub between coats.

But even with a coat as light as I can apply it, and a light cut/mix (i.e. less than 1.5lb), I end up with a residue in some areas, which looks a bit like tide marks (see photo).

So, two questions:
  1. Why am I getting these marks? Wrong type of applicator? Shellac mixture gone off?
  2. How can I remove them? Will pure meths do it? Or do I have to go mechanical?
I read or watched somewhere that subsequent coats of shellac dissolve previous coats, but these marks are not going away even with additional coats.
 

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eribaMotters

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I'm trying to figure out why you want shellac over boiled linseed oil. Iv'e used Danish Oil on Iroko, Teak, Oak and Ash, sometimes waxing over the top a week or so later. I've had no issues with this method and results have always looked fine.

Colin
 

fiveeyes

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I used shellac over BLO, with nary a problem. But, I used rattle can spray, which is de-waxed, or it would not spray. After the shellac, came wax.
 

Cabinetman

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I also am curious as to why you would put Blo on the timber before you start to French polish, A touch on the rubber as you apply the shellac maybe, I seem to remember reading that if you use too much BLO on your rubber it rises to the surface as you French polish and it spoils the finish, maybe that’s what you’ve got.
 

profchris

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I've seen that when shellac is applied too thickly. You need lots of thin, even coats, not a few thick coats. The problem is that the thick coat appears dry, but in places isn't. When you apply another coat over the top, it softens the whole thing in those places and the shellac then starts to flow around (no idea why, but it does). I've had waves like that, and also holes with the shellac heaping up on either side.

Multiple thin coats is quicker anyway - I can apply maybe 4 thin coats in a day but only 1 thick coat, and I'd still be at risk with the thick coat if I applied another the following day.

I have no experience with BLO under shellac, though the shellac should adhere if the BLO is properly cured before the shellac is applied. Long term, the soft BLO layer might move an crack the hard shellac layer, though if the BLO layer is very thin then you could be OK.
 

Sgian Dubh

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Looks to me as if the polish has been too thickly applied on the edge and it's run down and along the wide surface. Possible cause might be dragging the brush on to the flat surface from outside the edge rather than dragging the brush from the centre of the panel towards and off the edge. Slainte.
 

kinverkid

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I would have to go with what profchris said. It should take to the oiled surface if it was given long enough to cure. It would probably take over a week if your workshop is as cold as mine. Glad you said it was teak before I wrongly identified it as mahogany.
 

Sgian Dubh

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Looks to me as if the polish has been too thickly applied on the edge and it's run down and along the wide surface. Possible cause might be dragging the brush on to the flat surface from outside the edge rather than dragging the brush from the centre of the panel towards and off the edge. Slainte.
On reflection, I'm not sure I've assessed the problem correctly. I'm pretty sure I'm correct to say there's been a build up of polish on the flat surface leading to the tide like markings, but I think I've got the mechanism, as described above, wrong. Whilst what I previously described does lead to fat edges and blobs of finish, I don't think this is what has happened here.

More likely, I suspect, is that what we're seeing is the second face to which the polish was applied. If the unseen face had polish applied first with that face sat upwards, along with applying polish to the edges, then with a build up of polish on those edges some of that polish could run down and along the face, caused by surface tension in the wet polish, and we see photographed. Later, when the panel was turned over and polish applied to that face it would also be applied over those blobs of polish that had run along that face from the edge previously polished.

Anyway, I'm still not sure I've got it right, but I think what I've described is a possibility. Slainte.
 

dzj

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If you're brushing it on, perhaps a little heavier cut and lay the piece on a level surface.
 

JonOuk

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Linseed oil is supposed to be a lubricant when fadding (using a rubber) on shellac.
The thinning of the pullover on the final coats, let’s the oil come to the surface and not get trapped in the shellac.
That’s what I was taught at college anyway lol
 

JonOuk

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Not sure what you mean... are you talking about the darker semi circular marks on the left hand side? Are they greasy after the shellac has gone off?
 

pe2dave

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Linseed oil is supposed to be a lubricant when fadding (using a rubber) on shellac.
The thinning of the pullover on the final coats, let’s the oil come to the surface and not get trapped in the shellac.
That’s what I was taught at college anyway lol
How were you taught to use the linseed please? Mixed in, prior to...?
 

cookiemonster

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Thank you very much for all your help and sorry I haven't been back before now - been finishing work stuff before the Easter break.

It's sapele, not teak. My mistake.

But I don't think that makes a difference.

The photo (a close up of the underside of the tabletop near the edge) could indeed show the outcome of the shellac running off from the table surface when wet. But I also got similar marks on the tabletop itself.

It's annoying because, as I said, I used a light cut and applied it as thinly as I could. And the BLO had cured for ages before I did it.

Perhaps the brush I'm using carries too much liquid? I'm using a gloss paint brush.

Perhaps the brush was contaminated.

Pure meths doesn't remove the marks so I'm going to have to sand them off, or perhaps use a card scraper.
 

pe2dave

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Others I have seen use a quite fancy, very flat brush (possibly this?) Does it really make a difference?
Any sources for such a reference please?
 

Cabinetman

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Thank you very much for all your help and sorry I haven't been back before now - been finishing work stuff before the Easter break.

It's sapele, not teak. My mistake.

But I don't think that makes a difference.

The photo (a close up of the underside of the tabletop near the edge) could indeed show the outcome of the shellac running off from the table surface when wet. But I also got similar marks on the tabletop itself.

It's annoying because, as I said, I used a light cut and applied it as thinly as I could. And the BLO had cured for ages before I did it.

Perhaps the brush I'm using carries too much liquid? I'm using a gloss paint brush.

Perhaps the brush was contaminated.

Pure meths doesn't remove the marks so I'm going to have to sand them off, or perhaps use a card scraper.
Hi, I think it might be because you’re using a brush, it’s quite a thin liquid isn’t it so I think it’s running off too heavily from your brush,, if you don’t want to do it the old-fashioned way with a rubber impregnated with the shellac it might be a case of put it on quickly with a dryish brush and then spread about/ take off the surplus with a rubber or just a piece of cotton (old shirt) with some kitchen towel or cotton wool in the centre. A rubber like this can be kept in a sealed jar for months btw. Ian
Others I have seen use a quite fancy, very flat brush (possibly this?) Does it really make a difference?
Any sources for such a reference please?
Sorry wrong quote, but in answer to your question Dave I’ve always just put a dab on the rubber from my finger dipped into the linseed oil, decanted into a lid or similar, The difference it makes is like when you rub candle on your plane sole. Ian
 

profchris

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I've just remembered- I learnt only to brush from the centre to the edges. Bringing the brush *on* to an edge pulled a lot of shellac off, causing runs.

Might that be the cause?
 

JonOuk

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How were you taught to use the linseed please? Mixed in, prior to...?
(I’ve not actually had to do it in 20 odd years,so I may be remembering it wrong tbf!)
I’m sure it was added sparingly to the rubber, think it may have even been raw linseed oil, not boiled 🤔
 
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