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Essential W o o d c a R VIN G Techxiques

accclcratcd process in a chamber wherc che atmosphere around che wood is artificially controllcd, scarting with cool steam and moving ac a pace sec ouc in schedules varving wirh differenc timbcrs to warm dry air. This takcs only wceks. The schedules arc quitc accuratc nowadays but, because of the variability of wood, rhey are not infalliblc. Air drying, on the other hand, cakes about one year for every 25mm (1 in) of thickness, and is very unlikely to reduce the moisture in che wood to a State when it is dry enough co be safely taken into a centrally heated building. Some woods take even longer to dry, especially if kept in the log.

Seasoned Wood - Moisture CONTENT

The proccss of drying the wood is called seasoning. Seasoned wood does not mean much unlcss one knows what it is seasoned for. Ifyou buy expensively dried timber with a moisture content (MC) appropriate to a centrally heated house and use it for outdoor sculprure, you are wasting money. Converselv, if you buy unseasoned wood and put it into a dry workshop, you are invicing disaster. The MC of wood gives the weight of the water that is in the wood as a percentage of che weight of the wood materiaÅ‚. A smali sample is weighed, then dried in an oven for about 18 hours at a fcw degrees above the temperaturÄ™ of boiling water. When it has stopped losing weight the dry weight is subtracted from the wet weight, divided by the dry weight and multiplied by 100. The fibrÄ™ saturation point, where all free water is lost and the bound water starts to be released, is around 30% MC. In a British summer, air-dried timber may go down to about 14%. A centrally heated house will rcquire an MC of around 11%. This is useful information when one bcars in mind that moulds and fungi require at least 20% MC to survive, and wood bcetlcs cannot breed in wood at less chan 10 or 11% MC.

Seasoning Wood for Carving

Many carvers acquirc wood in log form rather than seasoned bÅ‚ock, and wish to kecp it in as large a piece as possible. The usual advice is to remove the bark, paint the ends and lay it horizontally on blocks where the outside air can circulate freely but the rain and sun cannot reach it. Keeping it in a shed or garage may ruin it if the place becomes an ovcn when the sun shines. Some timbers do not season well, but if they are first split or sawn lengthways into halves or quarters they will dry faster and with less splitcing. They will probably distort, so if they are planed and glued into their original position when dried the partem of che grain may not fu perfectly. This, however, is preferable to any other form of building up if the figurÄ™ is imporcant to the carving. I usually keep one or rwo pieces ac least 450mm (18in) long in the log and cleave or, with the saw, halve or quarter the rest. If the ends have been exposed for a day or rwo I paint them with a disinfectant such as dilutc Jeyes Fluid or a fungicide on the exposed surfaces to kill off fungus spores, which are omnipresent, before sealing the ends (Fig 2.15).

Drying Problems with Particular Woods

Some good carving woods such as laburnum {Laburnum anagyroides), holly, pear (Pyrtts conwmnis), cherry (Prunus avium), plum (Primus communis) and applc {Malus spp.) are very dense and dry badly. I have found that, if these other conditions are observed and rot has not yet begun, leaving the bark on hclps but makes the drying evcn longer. Apple and bccch {Fagus syhatica) particularly need watching for signs of woodworm. Another method is to rough carve the intendcd sculpturc and leave it to dry or, if it is all to be very rhin in section when finished,

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