WOODWORKERS'  ASSOCIATION  OF 
NEW SOUTH WALES Inc.
February 2003 Meeting
Finishes on Timber

All the wood in your home came from a tree
that gave up it's oxygen generating life for you,
the least you can do is show it some respect.    Anon.

We are living in a world today where lemonade is made from artificial flavours
and furniture polish is made from real lemons.    Alfred E. Neuman

Monday 3 February 2003: 
Presenter: Lindsay Skinner, Wooden Comforts Pty Ltd, Annangrove

Lindsay Skinner has been a furniture maker, wood turner, and French polisher for 30 years.  Wooden Comforts Pty Ltd, Annangrove, has designed furniture and made to others' designs, done production work for various companies, and has restored thousands of antique and contemporary pieces in many different finishes and special effects.

Economics requires that most finishes are sprayed;  although some are hand applied.  The required finish depends on the proposed use of the item - a trophy would be displayed and admired but rarely handled, whereas commercial items need a hard finish to withstand public abuse.  Nitrocellulose lacquers can be retarded and brushed on, even on a lathe turning slowly.  Low vapour emission from the finish must be considered from a health perspective.  Water-base finishes (Cabot, Speed Clear) are OK but speed of drying could be a problem.  Cabot is hard.

Single-pot polyurethanes are thinned (1st coat to 50%) with turps.  BEWARE of silicones used to improve the flow.  Removal of silicone is a pig of a problem.  Instead, heat the tin in hot water, even over a burner, and any bubbles will easily come to the surface.  It can be coloured with up to 10% spirit stain;  but turps-based stains are better (Estapol + stain).  For Opera House counters, Wattle was too soft;  Cabot with additive was harder.

Dust deposition during drying was of major interest to the audience.  Floors should be dampened with water and detergent. Negative Ion Generators (See Telstra Yellow Pages under Air Purification Equipment) were recommended for ‘pull-down' of woodworking dust, as with smoke in clubs and for children with asthma.  Commercial units are $200 and up, but small units are $29 from Jaycar (6 stores around Sydney).  To minimise dust settling, table tops should supported at a steep angle for finishing and drying.

Two-pot polyurethanes were said to give off vapours (isocyanates) for 4 years and to be hard to repair, cracking if dropped, (whereas lacquers are easy to repair).  A high-gloss finish can be obtained with car polish on top.  Crystal Veneer by Wattle has no wax.

Imperfections can be rubbed with shellac and vinegar.  Alternatively, before the finish has gone rock hard, use the paper back of abrasive paper with water and detergent lubrication.  There is no scratching as with even warn-out 320 grit paper!  Also 3M has rubber-impregnated backing paper.

Abrasives:  Steel wool should not be used because of a grey substance which is left behind.  3M Bear Tex is available  in grades of red (with carborundum), green, brown (vicious), white.  It is also useful for cleaning tiles, glass, etc. and, with WD 40, for removing rust from machinery.  A 50-75 mm wide strip is about $9/metre.  Try SA & S Stimson Pty Ltd, Balmain.

Oil Finishes like Penetrol and Organoil are not quite up to furniture quality.  A harder version of Organoil is made for floors.  Again, these can be thinned for penetration.  Penetrol, like Danish oil, can be thinned with turps but the vapour problem and a nasty smell can remain for 4 years.  Livos products (Livos Phytochemistry of Germany) have natural, thinners, citrus, and are recommended by the Bungendore gallery.  Sprayed oils can darken somewhat, showing orange on light woods - better on darker timbers.  Linseed oil, despite driers can be reactivated by heat or sunlight.  Steer away from Scandinavian oil - print from newspaper can transfer!

Stains and fillers can be oil, water or spirit-based.  Oil-based products dry overnight (or 8 hours), water-based products are only used to match existing treatments.  Spirit-based products are used commercially on account of their faster drying.  All will draw the grain of the timber;  accordingly always dampen surfaces slightly with water, allow to dry, and sand.  Proceed as follows:  Dampen and resand;  stain to half requirement;  add finish + rest of stain.  Because the colour is in the finish it has more depth and looks professional.  Pinus Radiata is resinous so use oil-based (not spirit-based) products to avoid a patchy result.  Plastibond stopper and Jetflex (hard) are suitable for repairing blemishes but beware the possibility of light spots.

Dark woods, e.g. Jarrah, Blackwood, Mahogany, if dampened, can discolour or even blacken due to tannin so use methylated spirits, not water.  A new Wattle product Wood Gel is good also for Radiata.  The 3M 9310 Protector Safety mask was recommended for comfort and performance.  Gas mask devices are a hot weather problem.

Shellac is available as buttons or flakes and dissolved in methylated spirits.  Button shellac builds faster needing only 5 coats as against 10-12 coats with flake shellac.  Button shellac is used to fill holes by melting with a cigarette lighter.  Shellac thinned to 50% is used as a sealer, particularly for edges, e.g. of craftwood.  Most finishes, e.g. wax, can be applied over shellac.  But sanding sealers should be avoided as subsequent mechanical damage will show through as a white mark.  Shellac does not become opaque or milky - the first thin coat soaks in and provides a chemical key, e.g. for polyurethane or water-based finishes.  It can be sprayed, at low pressure, left overnight, cut back and rubbed to a beautiful finish.

Ready-mixed Shellac is available also, in white (bleached and granulated) and blonde (dewaxed).  But it can conveniently be made as required by taking a jar half full of dry material, adding methylated spirits and possibly an oxide pigment and leaving overnight before further dilution.  Then strain it through pantyhose.

Gloves, at $ 3 for a packet of 10 are an affordable necessity.  Finger stalls (dressmakers') are useful, as are kidskin gloves or gloves without fingertips.

Cork blocks are traditional for sanding, but rubber blocks (car repair industry) can be left in water and stay flat - or blocks can be made from Clarke foam rubber.

Finished timber products should not be exposed to sunlight in transport.  Finished surfaces face-to-face should be separated carefully with waxed paper - otherwise the surfaces will be glued together!!  But do not use tissue paper as it causes fine scratches.

Abrasive gauze (from the surfboard industry) can be used for rapid surface abrasion of dampened timber.

Application of finish should be in long strokes, not back-and-forth.

Tack rags (from the automotive industry) are greasy;  alternatively wash old singlets, rinse in kerosene and peg out to dry - the mineral oil helps in the removal of surface dust.

Rubbers can be made from industrial cotton wool (like upholsterers lint) teased up and held in handkerchief-sized material.  Shellac, e.g., is added and squeezed out to give the desired application rate.

Drying Agent:  Try Terebine (by Feast Watson), a lead-free resin-based drier for oil-based paints and varnishes (not suitable for polyurethane or water-based paint).  Mix ratio 1:16.

Pencil Lines must be removed, but not with abrasive - use a large pencil eraser!

Wax:  Liberon Black Bison paste wax was recommended over any finish (Liberon Enterprises, Fyshwick, ACT - www.liberon.com.au/order.htm) - try Stimson's.  But first fine rub back or use white Bear Tex (3M).  Wax can also be used to lubricate a bandsaw table - wash off with a turps rag.

Black Japan (by Feast Watson) is a jet black (but can be diluted with turps).  Other colours, blue, orange, red, primaries, brown are obtainable - try Stimson's.  Oxides are available from cement sources and pottery glazing sources.

Yellowing due to UV effect can be stopped with polyurethane + white pigment (oil-based from artists' suppliers).  Wattle Speed Clear is a water-based Estapol, milky in the tin and claimed to be non-yellowing (thin with 5% water 1st coat only).

Liming white (oil-based) was not recommended due to discolouration;  however water-based or turps-based liming is used (see Feast Watson Liming Solution).  Even thin acrylic paint is good on light timbers.

Scrapers by Sandvik were recommended, but scrapers can be made from worn-out hardened-tooth saws.

Getting rid of Silicone is very difficult, even with white spirits.  It also occurs naturally in Teak.  One sure method is to wipe the surface with methylated spirits on a rag;  then stand back and light it (the surface, NOT the rag!).

As reported by Frank Duff 
 

Copyright © WOODWORKERS' ASSOCIATION OF NEW SOUTH WALES Inc. 2002