January 2002 Demo

Questions and Answers 5th January 2002

(Editor’s note: I missed this meeting so when I read what William O’Callaghan had so carefully recorded I thought it was worth printing here in its entirety. I hope you agree.)
In this first meeting of the New Year we enjoyed an informative question and answers session during which Henry East, Des McMahon, Mick Healy, Harry Kampff. Hugh Flynn and Joe O’Neill allowed their brains to be picked.
The topic of drying/seasoning timber for turning is one of enduring practical interest and the panel all had useful advice to offer.
If timber is to be dried naturally then according to Des McMahon the most important thing is to avoid exposure to the sun. The ideal arrangement is an open airy shed; leave the bark on and seal the cut ends with wax, paint, Polybond etc. – the object being to slow down the evaporation of moisture. Mick Healy added that timber should be stored in the dark and that ideally timber should be stored on end for as long as possible – one is talking about a year for each inch of thickness. Joe O’Neill recommended that logs should be split on a diameter as soon as possible after felling and the cut surfaces sealed.

As an alternative to traditional seasoning methods one might consider artificial drying. Des McMahon described having had some success with a home-made kiln. This consisted of a 5 cu. ft. box made from ¾ inch chipboard, insulated with 1 inch Aeroboard and kitchen foil and with an air vent. The box is equipped with a 50 watt heater and the temperature is controlled at 90 deg. F by a thermostat from a fish tank. Des found timber will dry to a satisfactory state in 3 or 4 weeks. One can judge the drying progress by weighing the timber at the start and keep drying until there is no further weight loss. He mentioned that drying should not be taken too far as the timber will become too hard and this makes it prone to splitting and turning could be hazardous.

One can also use a microwave oven to dry timber. Mick Healy would only use a microwave for rough-turned items as solid timber will crack. He advises putting a cup of water in the oven, operate at maximum power for 2 mins and then let the item rest for 10 mins. As there will be further moisture loss in this period. one should weigh the item before drying and continue drying until the weight stabilises. Des McMahon reckons that items rough-turned to about ¼ inch thick can be dried in a microwave at ‘defrost’ in about 3 mins. – it being advisable to change the position of the item from time to time. Joe O’Neill warned against over-drying which can result in cracking or even disintegration while turning.

Mick Healy suggested one could try boiling the timber or placing it in flowing water in order to wash out the sap which is quite viscous.
Des McMahon pointed out that it is quite difficult to avoid twisting and cracking as timber dries and that as an alternative to drying timber one can turn timber while still wet. If, for example, a bowl is rough-turned to a wall thickness substantially greater than the finished thickness – say 1 to 11/4 inches- the rough-turned bowl may twist and distort but cracking is avoided and when the moisture content has stabilised it can be finished-turned.
Joe O’Neill thinks it is best to rough-turn wood quickly and both he and Henry East mentioned that one needs to give some thought as to how the rough-turned bowl can be re-chucked for finish-turning.
Changing topics - one does not have to use a chuck when turning a bowl, it is often better to mount the workpiece on a faceplate as it is more stable and there is less vibration.

Hugh Flynn suggested gluing a sacrificial block to a faced surface which will ultimately become the base of the bowl. One can use hot-melt or super glue. If using hot-melt glue one should warm the block and the blank -(hair drier is good but ask her first, for the sake of safety) before applying the glue and then clamp them together for the 2 or 3 mins. The glue needs to set. He had used this technique after the outside of the bowl had been finished with Danish oil and had found the glue adhered quite satisfactorily to the oiled surface.

Finishing is a topic which always arises at a questions and answers session. Hugh Flynn said that ideally one should try to get the best finish one can from the tool and this means that tools must be really sharp. His usual practice is to start sanding with 80 grit [occasionally 60 grit] and then continue with finer grits: 120, 180, 240 and sometimes 400. His preferred finish for bowls is Danish oil; for small items he prefers cellulose sanding sealer followed by wax.
Finishing end grain on the insides of bowls can present problems. Possible solutions are to use shear scraping to remove ridges and it is worth trying an application of paste wax when turning and sanding. Hugh prefers Liberon to Briwax for this purpose. Mick Healy suggested applying sanding sealer before the last cut with the tool and follow with a further application of sanding sealer before finishing. In his experience end grain can be finished very quickly with power sanding.
With regard to power sanding Joe O’Neill gave a useful tip for a DIY sander. From an old inner tube cut a disc of the reinforced rubber from around the valve, the disc can be held in a drill chuck by the valve tube.

Henry East, referring mainly to finishing bowls, uses Danish oil almost exclusively. His method is to apply the oil generously to the stationary workpiece so that it is saturated. After 2 or 3 mins. the surface is dried off with a dry cloth [preferably a paper cloth] using light pressure and with the lathe at a low speed, say 450 rpm. When the surface is almost dry stop the lathe and leave the work for 24 hours to dry off completely. Henry then repeats the above process but runs the lathe at higher speed and applies the dry cloth with greater pressure and for a longer time. He will usually repeat the process once more and he finds 3 coats are usually satisfactory.
In his experience Henry says some timbers [e.g. yew] will not absorb Danish oil easily and for these he prefers to use liquid paraffin using the same technique as with Danish oil. A useful tip: cheapest source for liquid paraffin is a veterinary supplier.
Henry says he does not usually sand between coats but may, with the lathe stopped, ‘polish’ the surface with 0000 grade wire wool using a figure-of-eight pattern as in French polishing.

Joe O’Neill said that sharp tools were essential and that some timbers particularly exotic timbers, yew and laburnum needed little further finishing. It is possible to stabilise soft areas with super glue but it is expensive and he would only use it for repairs. Joe advises application of 50/50 sanding sealer prior to sanding and he would start with 80 grit. He mentioned the importance of keeping the paper moving all the time.
If using spalted beech Mick Healy advises using sanding sealer all over in order to deal with soft spots and as a further refinement Henry East suggests allowing the sanding sealer to dry off and harden before applying oil etc. as this prevents the spalting bleeding into the surrounding timber.
Turners selling their wares at craft fairs will be relieved to hear from Des McMahon that the items that have been traditionally sold at craft fairs seem to be as popular as ever and that he has noticed no radical change in customers’ taste.

Our many thanks to the panel and to the members who participated in the discussions.

William O'Callaghan