Strange marks on a bowl

[WoodMangler]

I have some odd marks I don't understand. I've turned this bowl from tulipwood (first time I've used it), about 6-1/2" diameter. I turned it in the usual fashion. I sanded to 600 grit, mainly with a rotary sander, and then Nyweb'd it to yellow (which is, I think, 1000 grit), I applied shellac sanding sealer before the final yellow nyweb. I then washed it off with white spirit. At this point it showed none of the marks that have me puzzled. I then applied 4 coats of boiled linseed oil - apply thickly, wipe off excess after 1/4 hour, re-apply after another hour. This is the first time I've tried an oil finish, previous turnings have all been finished with a polish of some kind.

I've ended up with two light marks running across the bowl - in the upper picture it's left-to-right, and the lower picture it's top-to-bottom. The marks occur in the same place on both sides of the bowl. Are these marks to be expected and, if not, is there any way I can get rid of them before I apply my final polish ?

 

[Bodrighy]

I use a lot of this as I get offcuts from a furniture factory. The wood can vary in colour from dark green, almost black throuigh to almost white and often has these odd streaks of colour through them. It doesn't always show until you cut it. Not sure of the reasons but the furniture fasctory wants the white stuff so reject the darker coloured pieces .
P.S. nice clean looking bowl, colouring just lifts it IMHO.

pete

 

[paulm]

Looks like it's a feature of the wood rather than a finishing issue ?

I use oil finishes a lot, wouldn't normally use a sealer beforehand though as it will reduce the penetration of the oil into the wood. I also leave the piece at least twelve hours between coats, often twenty four hours, before re-oiling to give it a chance to cure before re-coating. More than one way to skin the proverbial though

Cheers, Paul

 

[andersonec]

Wierd!!! Was your White spirit dry before you applied your oil? I can only guess that there is something preventing the oil being taken in at the same rate as the rest of the wood, failing that, was it sat in the sun and something cast a shadow where the light patch is and not allowing that section to fade evenly? If it is bothering you then I would try re-chucking it and try again with the white spirit, if the oil is too dry to remove with spirit then scrape or sand.

Andy

 

[Bodrighy]

The fact that the colouring is in the same place on both sides of the bowl surely tells you that it is the wood, not the finish? As I said, I use loads of this wood and it is perfectly normal to have different coloured marks through it. Often, with any wood, adding a finish will highlight what at first is not that noticeable.

Pete

 

[WoodMangler]

Thanks folks. Nice to know it probably wasn't something I did :wink: I'll assume it's natural and go ahead with the polish when the oil is dry (in a couple of days). Andy, what is this mythical 'sun' of which you speak ?

 

[CHJ]

....... I applied shellac sanding sealer before the final yellow nyweb. I then washed it off with white spirit. At this point it showed none of the marks that have me puzzled. I then applied 4 coats of boiled linseed oil - apply thickly, wipe off excess after 1/4 hour, re-apply after another hour. This is the first time I've tried an oil finish, previous turnings have all been finished with a polish of some kind.

I think the light marks are a function of the wood growth that have been highlighted during finishing.

Basically I would question your approach to finishing, as mentioned already it is not normal to seal a wood prior to oiling, but straight oiling is likely to show such wood texture faults from growth stress lines etc. anyway. (different absorption rates)

Shellac is a spirit based solvent finish, (methylated spirits) White Spirit is not the normal solvent and may have been an added factor in influencing the absorbent characteristics of the wood fault. The colour difference may fade if solvents left to thoroughly disperse.

Burnishing the wood to 600 grit before sealing or oiling I would also question, if you want a polished surface you need a good sealed coating or fully polymerised oil coating, both of which will bond better if only sanded to the texture of the wood in my experience and rarely needing better than 240 grit, and then polish this hardened surface.

 

[andersonec]

Thanks folks. Nice to know it probably wasn't something I did :wink: I'll assume it's natural and go ahead with the polish when the oil is dry (in a couple of days). Andy, what is this mythical 'sun' of which you speak ?

Did you not hear the news??? it's been the sunniest winter for ninety years.

Andy

 

[WoodMangler]

Basically I would question your approach to finishing, as mentioned already it is not normal to seal a wood prior to oiling, but straight oiling is likely to show such wood texture faults from growth stress lines etc. anyway. (different absorption rates)

I'm still a beginner at this, all advice gratefully received. The only reason I used sanding sealer was to tame some wild grain that I couldn't get rid of any other way.

Shellac is a spirit based solvent finish, (methylated spirits) White Spirit is not the normal solvent and may have been an added factor in influencing the absorbent characteristics of the wood fault. The colour difference may fade if solvents left to thoroughly disperse.

I used white spirit to get rid of any lingering sawdust, as I do with painting softwood. I'll remember not to do that in future.

Burnishing the wood to 600 grit before sealing or oiling I would also question, if you want a polished surface you need a good sealed coating or fully polymerised oil coating, both of which will bond better if only sanded to the texture of the wood in my experience and rarely needing better than 240 grit, and then polish this hardened surface.

Thanks. I'll try that approach next time.

 

[CHJ]

..I'm still a beginner at this, all advice gratefully received. The only reason I used sanding sealer was to tame some wild grain that I couldn't get rid of any other way.

Best practice is to use the same product you intend to finish with, if in doubt use water to swell and raise grain and allow to dry when finished.

......I used white spirit to get rid of any lingering sawdust, as I do with painting softwood.

You may get away with it with some finishing oils that use it as a solvent but best avoided as it can soak into the wood and if not fully dispersed before applying alternate finish could result in poor adhesion or blotchy appearance. Best use a tack rag or the same solvent as the subsequent finish. I just run a cheap soft washing up brush over the piece on the lathe before applying sealant.

Although this post is about using a buffing system the finishing process is the same if you use very fine abrasives or burnishing cream on a hardened sealed surface. Of course you may not wish to have a highly polished surface but the sanding regime does not need to be any finer than the natural wood texture as long as you sand with the grain and do not leave cross grain scratches. Nothing in this thread has been sanded below 240 grit.

 

[WoodMangler]

I also leave the piece at least twelve hours between coats, often twenty four hours, before re-oiling to give it a chance to cure before re-coating.

I have a follow-up question, which is probably stupid but I'll ask anyway :wink: - when you've applied the oil, do you wipe the excess off after a certain amount of time, or leave it for the full 12 hours ?

 

[CHJ]

Wipe any pooling off after a few minutes, otherwise you are going to get thick, possibly wrinkled skin isolated islands of oil.

By wiping off surplus you are encouraging an even layer of polymerised oil to evenly seal the wood surface so that the next coat is absorbed or blocked from absorption more evenly.

 

[WoodMangler]

Wipe any pooling off after a few minutes, otherwise you are going to get thick, possibly wrinkled skin isolated islands of oil.
By wiping off surplus you are encouraging an even layer of polymerised oil to evenly seal the wood surface so that the next coat is absorbed or blocked from absorption more evenly.

O.K. - thanks.