sealing green bowls ?

[iggy37]

hello,
I am new to turning and am taking the" teach myself "approach to it which is foolhardy perhaps but very rewarding at the same time !.
I have turned a few bowls now and seem to be having trouble with cracking wood as it dries. I now understand that maybe i should be sealing my bowls prior to drying could someone please tell me what i should be sealing them with and where can i purchase it ?
I am in devon near barnstaple.
Thanks,
Iggy.

 

[CHJ]

Welcome to the forum.

If you are turning green wood then there are two basic approaches.

1. Turn it as thin as possible to an even all over thickness (2-4mm) and watch it deform, hopefully without splitting as it dries.
2. Rough turn it to shape leaving wall thickness at about 10% of its intended finished diameter, say 15-20mm thick and put it to one side to dry in a controlled manner* so that it distorts but does not split. When dry finish turn to size.

*

To control drying wrap the outer shell in stiff paper or several layers of newspaper and stack it inverted to dry.
I loose about 5% to splitting and they usually dry out in 4-5 weeks.

Sealing won't work with green wood, treating with Lemon Oil will slow the loss of moisture and reduce the risk of splitting due to rapid moisture loss from differing grain orientation.

 

[Jacob]

Possibly dry them very slowly e.g. outside but under cover and well shaded from the sun.
Sealing won't help IMHO.
There is the PEG approach - before turning (or very promptly after, but before finishing off) soak green wood in a PEG solution, which stabilises it.

 

[CHJ]

Link Here to some items turned from the green which gives an idea of the timescales.

 

[PsyMan]

One common new turning mistake I have seen is to attempt bowls from a cut log end (end grain) instead of splitting it down the centre line and using each half for a bowl (cross grain) as in Chas's informative picture guide, that will result in splits and cracks almost every time. Try to avoid leaving the very centre/pith in the bowl too as that almost always splits.

 

[Leo]

I sometimes use a watered down wood glue ( 5% glue ) brushed on the end grain, inside and out, this doesn't completely seal it, so it can still dry out, but more like the speed that the rest of it does. Maybe this also helps hold it together a little, but I haven't looked into that much. I also wrap in paper etc.

On some woods even prayers won't help :twisted: ( but I do live in a very hot climate, so my methods need to differ from some on here anyway )...................

 

[iggy37]

excellent help thankyou all . Newspaper at the ready along with crossed fingers ! :lol:

 

[robo hippy]

I turn thin, to finish thickness (1/4 to 1/2 inch max) let them dry and warp, then sand and finish. I used to do the paper wrap, which was a technique developed by those who use a DNA (denatured alcohol) soak to help the twice turned bowls dry faster. I now use some stretch plastic film on the outside rim to help prevent cracking. Do round over the rims, and really stretch the film out. A bit of compression on the rim really helps prevent cracking. Pacific Madrone is the most difficult wood I have found to dry without cracking issues. The stretch film has done wonders for success rates with this wood. Madrone warps insanely. I had one bowl I turned at Christmas time. Came off the lathe at 22 inch diameter. Finished warping at 25 by 17 inches.

I do use a LDD bath (liquid dishwashing detergent, the cheap brown stuff mixed 50/50 with water, soak for 24 hours, rinse off lightly, wrap the rim) for my bowls. It does nothing for drying times, warping or cracking, but does a lot to make even difficult woods a lot easier to sand out. Thin turned bowls are dry in about 10 days max. I do start them out on the floor for a few days, then up on some wire shelves for the last few days.

robo hippy

 

[OldWood]

I turn thin, to finish thickness (1/4 to 1/2 inch max) let them dry and warp, then sand and finish. I used to do the paper wrap, which was a technique developed by those who use a DNA (denatured alcohol) soak to help the twice turned bowls dry faster. I now use some stretch plastic film on the outside rim to help prevent cracking. Do round over the rims, and really stretch the film out. A bit of compression on the rim really helps prevent cracking. Pacific Madrone is the most difficult wood I have found to dry without cracking issues. The stretch film has done wonders for success rates with this wood. Madrone warps insanely. I had one bowl I turned at Christmas time. Came off the lathe at 22 inch diameter. Finished warping at 25 by 17 inches.

I do use a LDD bath (liquid dishwashing detergent, the cheap brown stuff mixed 50/50 with water, soak for 24 hours, rinse off lightly, wrap the rim) for my bowls. It does nothing for drying times, warping or cracking, but does a lot to make even difficult woods a lot easier to sand out. Thin turned bowls are dry in about 10 days max. I do start them out on the floor for a few days, then up on some wire shelves for the last few days.

robo hippy

Hi RH - that's a good input.

Two questions - the 'stretch film' ; is that what we would call 'cling film' in the UK - comes in a roll to be mounted in a dispenser for wrapping food or sealing over the top of a jar ?

I've seen articles about the detergent use - do I take it that you turn the blank and then soak it, or do you soak the blank and then turn ?

Many thanks
Rob

 

[CHJ]

.... I used to do the paper wrap, which was a technique developed by those who use a DNA (denatured alcohol) soak to help the twice turned bowls dry faster. ....

That's where I started using the wrap to even up the moisture loss, after extensive comparisons over several months I found soaking in DNA only speeded up the drying time by 2-3 days at most for me, so abandoned the messing with it and just wrap.

But Local climate, drying area and its humidity etc. have a big effect on timeline and results.

 

[chrisbaker42]

Is cling film preferred to wrapping in newspaper?

 

[CHJ]

Is cling film preferred to wrapping in newspaper?

Try both !

Never compared results myself but a lot depends on your preferred drying location and speed of drying required, or should I say speed of drying that you can get away with. what may be viable near the coast or in a warmer climate may not be any good for someone in the middle of a big city in central land mass.

It's a case of suck it and see for each person and location I think because there are so many variables, some folks just stack them on the floor or the back corner of the shed with no wrapping and get away with it, mine are In a warm conservatory in the main and split if I don't take steps to slow things down. Cling film in the UK may encourage mold growth due to lack of air circulation.

 

[robo hippy]

The stretch film I use is the stuff they wrap around boxes on a pallet to keep the boxes from falling off. I get it at a local office supply place, or any place that has shipping supplies. Rolls are 5 inches wide and on a cardboard tube. Not too spendy. They do have wider rolls. The plastic food wrap stuff is similar, but you might want to check with the wife first before you raid the pantry.

I have never had problems with the mold. I wrapped the outside of a few bowls entirely in plastic just to see what happened. There was a small bit of condensation under the plastic for a day or two, but it went away. I figure that is because you leave the inside open. I find the plastic wrap better than the paper wrap. Paper wrap with the plastic on the rim works very well on drying bowls. Plastic wrap on the rim only appears to do the same job.

Drying is an art. I figure our weather here in Oregon is pretty similar to yours at least in winter, lots of rain, fog and drizzle. Pretty humid, so starting on the floor first, then raising it up to a shelf where it is a bit dryer later. Summers get warm here and dry, but morning humidity is high. I have never done the twice turned bowls, so don't really know how that works. I probably should try it some time, and experiment with the DNA soaking, sealing the bowls, plastic wrapping, etc. and seeing exactly how that all works.

As for the LDD soak, I turn the bowl, soak it, then let it dry. The LDD soak was first done by Ron Kent, a turner in Hawaii to help with sanding out the Norfolk Island Pine. I am not sure exactly what it does, but it makes woods like cherry easier to sand without it burning, or glazing over.

robo hippy

 

[chrisbaker42]

"Cling film in the UK may encourage mold growth"

Thanks for that Chas - not much good me using here in West Wales it's wet enough all the time without encouraging more dampness, I'll go with the newspaper.

 

[robo hippy]

Never had a mold problem, other than some I buried in green shavings.

I use this on thin turned bowls. Never attempted it on thick turned bowls.

robo hippy

 

[CHJ]

Never had a mold problem, other than some I buried in green shavings.

I use this on thin turned bowls. Never attempted it on thick turned bowls.

robo hippy

Yes, all techniques are worth exploring to see which best suits individual circumstances and woods, I've had pale white (twice turned) Birch and Sycamore pieces turn a dirty Grey [Gray ] throughout by being too slow in drying.

Lemon Oil seems a good way to go with thin items to add a bit of security from splitting and reduce the warping on the drying front.

 

[gus3049]

Yes, all techniques are worth exploring to see which best suits individual circumstances and woods, I've had pale white (twice turned) Birch and Sycamore pieces turn a dirty Grey [Gray ] throughout by being too slow in drying.

I'll second that. I am trying to make some hazel bowls at the moment and after rough turning the grey wood two months ago, it shows very few signs of changing, just one or two light patches. Got so frrustrated waiting that I left one out in the sun today to see what happens and nothing did! Just a wet patch underneath and its still patchy grey after five hours out there. If I try sanding it the paper clogs in seconds.

Robinia, dry in two weeks - no wrapping.

So it really is down to individual woods and experience it seems.