BobGilmour
9th August 2002, 12:29 AM
Hi everyone ... I am a free-form bowl and form maker .... (I snuck in here!! Sunglasses on. Fake moustache!! Funny walk. Didn't even see me did you??) ... full-time ... and also do small furniture, joinery and sculpture.
I know a lot of you turners do the same as me - turn ( = carve) green timber and then set it aside to dry before eventually finishing. A friend who is an accomplished turner says that a lot of the moisture gets slung out on the lathe ... however, he mostly on-sells wholesale to a gallery turner who completes the finishes (and puts his own name on the bottoms) - yukko!!.
Based on the northern tablelands in Far North Queensland, we have a pretty wide range of humidity conditions. During a lot of the year, humidity is fairly high, so drying is slow - good for fine walled bowls etc. I sometimes speed things up in the later stages by putting them in my airconditioned office - once a fair bit of the moisture has come out.
But, at this time of year, especially this year, we are getting relative humidities down in the 40's and 50's ... somedays lower. Which is abnormal. So ... hoping to hear from some southerners who are used to this sort of air dryness.
I normally rough down to about 12mm thickness in the walls of whatever I'm doing and the date the piece and place it in an air-dry rack along with a lot of other stuff. It's usually about 6 weeks before I do further work on any one piece. Just gotta be careful then to poke the pieces out of the racks with a stick or a big fork because taipans are pretty prevalent around these parts ... as are several other nasty snakes ... and they just love all the little stacks of cosy houses all stacked up under cover. So do the mice etc ... probably which attract the slitheries in the first place.
The eventual wall thickness of my work is around 3 to 4 mm up near the rims. Most of my bowls and platters have large flaired overhangs and small bases ... so there is a lot of thin wood there. Lots of waves and reverse curves etc. Up to around 900mm in diameter in some cases - depending on the wood blank (slab etc).
I'm wondering if there is anything special you turners do to control the drying process in the early stages of turned form drying when the humidity is very low. On the basis that too rapid drying in the early stages causes cracking and surface checking.
I have tried painting the roughed forms with Wattyl Speedclear - a water-based thin floorsealer - to slow down the moisture transfer - but with no intention of completely stopping it. I came up with using SpeedClear because it doesn't seem to penetrate too far ... and it's clear, so doesn't cause staining. This does seem to work fairly well for trunk and branch timber which has an actual grain pattern. However, I'm not convinced that it works as well for burl timber, which I have been having some trouble with of late -> this year is much dryer than any previous ones for us up here.
During normal climate times, my workshop is in an altitude area where the temperature is relatively cool and humidity relatively high. But, one of my selling locations is the Port Douglas market - where temperature is usually high and humidity can be anything. Therefore, there is always a tendency for work to open up if you don't get the finish and drying just right ... because of going from cool and humid to hot and sometimes dry. So, if there is still a substantial moisture content in the timber when I go through the finish stages (fine multi-product rubbed finish), checking is almost bound to happen in anything but the finest grained timbers.
Any exchange of experiences would be appreciated.
All the best
Bob.
------------------
wood's good
I know a lot of you turners do the same as me - turn ( = carve) green timber and then set it aside to dry before eventually finishing. A friend who is an accomplished turner says that a lot of the moisture gets slung out on the lathe ... however, he mostly on-sells wholesale to a gallery turner who completes the finishes (and puts his own name on the bottoms) - yukko!!.
Based on the northern tablelands in Far North Queensland, we have a pretty wide range of humidity conditions. During a lot of the year, humidity is fairly high, so drying is slow - good for fine walled bowls etc. I sometimes speed things up in the later stages by putting them in my airconditioned office - once a fair bit of the moisture has come out.
But, at this time of year, especially this year, we are getting relative humidities down in the 40's and 50's ... somedays lower. Which is abnormal. So ... hoping to hear from some southerners who are used to this sort of air dryness.
I normally rough down to about 12mm thickness in the walls of whatever I'm doing and the date the piece and place it in an air-dry rack along with a lot of other stuff. It's usually about 6 weeks before I do further work on any one piece. Just gotta be careful then to poke the pieces out of the racks with a stick or a big fork because taipans are pretty prevalent around these parts ... as are several other nasty snakes ... and they just love all the little stacks of cosy houses all stacked up under cover. So do the mice etc ... probably which attract the slitheries in the first place.
The eventual wall thickness of my work is around 3 to 4 mm up near the rims. Most of my bowls and platters have large flaired overhangs and small bases ... so there is a lot of thin wood there. Lots of waves and reverse curves etc. Up to around 900mm in diameter in some cases - depending on the wood blank (slab etc).
I'm wondering if there is anything special you turners do to control the drying process in the early stages of turned form drying when the humidity is very low. On the basis that too rapid drying in the early stages causes cracking and surface checking.
I have tried painting the roughed forms with Wattyl Speedclear - a water-based thin floorsealer - to slow down the moisture transfer - but with no intention of completely stopping it. I came up with using SpeedClear because it doesn't seem to penetrate too far ... and it's clear, so doesn't cause staining. This does seem to work fairly well for trunk and branch timber which has an actual grain pattern. However, I'm not convinced that it works as well for burl timber, which I have been having some trouble with of late -> this year is much dryer than any previous ones for us up here.
During normal climate times, my workshop is in an altitude area where the temperature is relatively cool and humidity relatively high. But, one of my selling locations is the Port Douglas market - where temperature is usually high and humidity can be anything. Therefore, there is always a tendency for work to open up if you don't get the finish and drying just right ... because of going from cool and humid to hot and sometimes dry. So, if there is still a substantial moisture content in the timber when I go through the finish stages (fine multi-product rubbed finish), checking is almost bound to happen in anything but the finest grained timbers.
Any exchange of experiences would be appreciated.
All the best
Bob.
------------------
wood's good