What sort of Finish?

[yvan]

We have a nest of three small walnut tables - at least I think is is walnut - made around the 1920's and the joints are glued with hide glue.

The finish on one of the tables is scaling the same way dry egg white would. It also looks like the top may have been varnished, judging by the dry "blobs" under the top surface.

What would be a good way to find out what was used? I have been thinking about using a metho/BLO/gum turpentine mix to remove the coating.
Am I on the right track?

All advice and/or suggestions will be gratefully received, thank you!

Yvan

[Xanthorrhoeas]

Photos would help yvan. Could be a range of finishes. The normal way is to test somewhere inconspicuous with a range of solvents. Obviously metho will remove shellac, lacquer solvents for those. Your mix does not sound the way to go to me. Boiled Linseed oil will get into raw timber and make it unsuitable for refinishing with shellac for instance. For that reason your mix is fine for cleaning off grime on an intact surface, but not for going down to raw timber.

[yvan]

Thanks Xanthorrhoeas, I will provide photos.

Yvan

[Luke Maddux]

I agree with Xanth, in that metho would be a good starting point. A piece made around 1920 has a very good chance of being polished with shellac, and the peeling/cracking you mention has me leaning that direction as well.

Either way, photos would be good. I look forward to seeing them.

Cheers,
Luke

[auscab]

What would be a good way to find out what was used? I have been thinking about using a metho/BLO/gum turpentine mix to remove the coating.
Am I on the right track?



Yvan

Linseed oil / metho and turps mixes , sometimes with vinegar added, are a way of cleaning off later polish jobs that are over original older polish jobs . They work great on things that have been heavily coloured later to cover faded finishes. The results are spectacular . They would be good for your use but knowing when to stop rubbing would be a little harder , not seeing a darker colour dissapear . You would have to test by scratching with a finger nail as your working it and when you see the top layer stop flaking off go a little further and stop .

The beauty of this method of removal is the very quick stripping action of the metho is slowed down and makes it more controllable by the oil and turps being there. And when you wipe it off, and buff dry, when you think its right, the oil and turps reacting with the metho leaves a smooth almost finished soft shine . Not a sticky jam like mess of half stripped shellac or spirit varnish mix .

If you did go all the way down to the raw timber , the effort you went to mixing up the mix would have been wasted as you may as well have just washed the lot off with metho in the first place.

If the mix did get into the raw wood though , wiping it off and letting dry a day would have no bad effects on a new french polish job . There is nothing wrong with linseed oil , boiled or raw, being rubbed into raw wood that needs to be polished as long as its well buffed dry and left a day . If its Raw linseed oil used leave it longer , maybe if it was a porus soft wood like Kauri pine , to be safe you could leave it a few days to a week .

Back in the 1860s grain filling was done a lot in the open Red cedar timber used here,and at the same time the trend for grain filling Mahogany the same way was used in the UK. After the plaster like paste with colour added was rubbed in and wiped off the piece was left to dry over night . The next day the chalky dry piece was lightly sanded then given a heavy wash in with boiled linseed oil and buffed dry again and left for another day or two before french polishing with shellac was started. As long as it was let dry off there were no problems.

Yes linseed oil trapped either in raw wood or in between layers of shellac causes later problems . milky white haze . White patches coming up or upper layers of shellac cracking and crazing all over . Just wiping off hard and letting dry is the answer though . If its not into raw wood and just on a sealed polished surface wiped off and polished straight away is fine .

The problem with oil in between layers of shellac comes from not wiping dry well enough and leaving the piece a day or three and the remaining film of oil starts drying off. When you get back to it ,You start polishing again over a stiff layer of oil that wont move off with the rubber or brush or rag applying the shellac, a fast hard drying plastic type of substance . And you have trapped a stiff but not yet dry film in there . This leads to white spots of off oil or crazing .

Ive tested and done this on purpose between shellac coats, and made it happen . I got the crazing effect and not the white off oil effect . Id expect the white effect happens because more oil may be trapped and it is well covered enough so that the oil doesn't have the strength to crack the shellac , the shellac being stronger. so it then goes off and turns white .

I used to work amongst a room full of polishers, one of whom had the re occurring problem of jobs coming back with oil issues . It took many years before I realized it was in the wiping off of the oil that was his problem . Before that I though it was the way he was finishing off with the oil . If the Older smarter French polishers knew they sure never told me at the time . I dont know what they said to him . The old polishers didn't just let anyone know how to solve a problem , esp a cabinet maker . Solutions were whispered in amongst themselves on the other side of the work shop.

Rob

[yvan]

Auscab,

Thank you very much for the detailed explanation of what will happen when some "left over" linseed oil gets trapped under shellac.

If I understand the process correctly, linseed oil which has penetrated the timber at let to dry is not the cause of the problem. It is the "saturated" oil remaining on the surface which will do the damage. From what you have said regarding polished pieces being returned, it seems that the reaction and whitening process occur relatively quickly.

So, does a "detergent" solution exist to wipe off this surface oil?

Yvan

[auscab]

Hi Yvan.
The whitening process takes some time to show up . It was between a month and three months roughly before we would see one of those mistakes come back . It happened over a three year period out of thirty years and was the result of one guy out of four polishers in that three year period of time roughly.
No detergent is needed , just wipe it all off with a dry rag and then take a second clean rag and try to get some more off the work onto that rag . Go to a third rag if needed.

I did used to give polish jobs a wipe with a rag with metho sometimes . Just after cutting back with oil and turps mix . You could try that.

The problem you can see on furniture of the vintage your trying to fix is , they can have later cheap polish jobs that were not just Shellac over the top of the original. Its a a spirit varnish mix which was part shellac and part varnish . Its a easy way out for the polisher . quicker with good fast results but is hopeless at lasting and is brittle and scratches easy as well as gets water damage easier. And almost too hard to revive depending on the amount of shellac in it . Washing back and starting again is the best way a lot of the time .

I cant tell from the picture if yours is spirit varnish or not . I cant see the usual spirit varnish problems with it though .

Rob

[Xanthorrhoeas]

I'm afraid I can't see any pictures for some reason. Rob obviously has lots of experience (more than I have in an industry situation), though I have seen oil damage develop over a few years even when the original oil has polymerised before the shellac is applied. I have a dining table that was "professionally" polished after oil had been used "to seal" the raw timber and it took five or more years for the finish to turn really milky. That is why I advise avoiding getting oil into raw timber.

Your mix, sometimes called Bristol Museum mix, is a great one for cleaning a dirty but intact finish. If there is an intact shellac (or other) finish under the muck then it's fine. I urge caution if there is not as it may bite you down the track. If you have slight oil penetration of raw timber applying turps tends to remove the oil and then soapy/detergent water will remove the turps. Wood turpentine smells lovely but should only be used in well-ventilated areas because it is dangerous to breathe (as is mineral turps but not as bad). As Rob says, letting it dry out well so whatever is in the wood can evaporate/polymerise and become stable, is very important, so take your time.

What you use depends on whether you are doing a clean off of an old intact finish or deliberately stripping the surface to raw to repolish.

For antique items the original finish is very important to the value of the item and should be retained if at all possible. For your items only you can decide whether you think they will be antiques of the future (retain original finish) or you just want them to be useable and look good (can repolish).

David

[yvan]

David,

I started a new thread in the Restoration Forum entitled "What sort of Finish? With Photos" on 31 Oct.
I didn't know how to post a reply and attach photos to it.

Thank you for your advice above.

Yvan