Razorback: a turned and carved project

Words and photos: Andrew Potocnik

During a demonstration, I once tried to cover several techniques in one piece. Combining green turning, carving with power tools and burning for texture and colour, I demonstrated the making of a bowl with a series of carved fins. I called it the Razorback bowl  – remember the feral pig in the film? There wasn’t enough time to complete the piece during the demonstration so I returned home with a partly-made disc needing completion. Here’s how I made the Razorback.

The back of the Razorback bowl

Roughing

I started by rough-turning a section of fresh or ‘green’ red gum to a discus-like profile, leaving a fuller curve on the eventual underside. I worked between centres, but it could just as easily be accomplished by using the tailstock to pin the blank against a scroll chuck, or by fitting timber to a faceplate.

A spigot was cut on the underside and the piece was then transferred to a scroll chuck. What would be the top was then trued and an opening cut made. The undercut allowed me to later reverse the form onto expanded jaws in order to carve out the under section.

The undercut and textured fins

Layout

I first drew the fins onto the upper surface. You can work freehand or use a circular object (or even a more flexible curve) as a template to trace around. I wanted the fins to appear as though they grew spirally from the circular opening, somewhat like a nautilus shell.

I drew the curves freehand, determining the spacing and size by eye. I often quip that I’m not a mathematician; therefore I’m not interested in working out measurements that are perfect! I prefer a ‘loose’ feel and was happy to combine this with a rough, textured finish. If you prefer a neater final result, you can position the fins more precisely and then sand to a smooth finish.

The re-turned collar and burnt sections – note how burning has softened the rough-carved edges.

Carving

An Arbortech minicarver fitted with an industrial blade was used to carve the fins. Carving on an angle gives an undercut effect which ‘raises’ the fins from the surface. As you work towards the outer rim, this angled cut will penetrate the rim. The fins are later shaped to a tooth-like, razor form. This can be done with a file or sharp knife.

Depending on the angle it’s held on, the minicarver can leave a fairly smooth surface, or you can create textured surfaces which can be accentuated by scorching. A cross-hatched pattern will result if you first pass the left side of the spinning cutter over the surface and then follow with the right side of the cutter. For maximum and safe control, I find it easiest to tuck my elbows into my sides and swivel my body. This also allows a controlled sweep across the surface of the wood.

Be sure the bowl is resting firmly on a flat surface so it won’t move once the tool touches it. I find it helps to hold it in a heavy chuck, such as a scroll chuck, which also holds it firmly when you reverse it to carve the other side. You can also use a jig similar to a carver’s vice.

Masking tape covers the fins, which are now spinning towards the toolrest. The base was removed and the fins cared right into the centre.

Before re-mounting the blank, I burnt around the opening. Don’t burn the entire surface, as the wood will dry and distort and then you won’t be able to turn it again. Any unwanted burn marks were removed when the opening was trued up and sanded. Be careful of those razor sharp teeth spinning around! You may choose to wrap packing tape or a section of car inner tube around the edge to protect your fingers, even though the teeth are pointing away from the rotation at this point. Two photos above you can see the re-turned collar and burnt sections. Note how the burning has softened the rough carved edges.

Hollowing and carving

The interior needed to be undercut quite severely, so I opted to use a heavy handled scraper. A Kelton hollower worked perfectly. Working from the other side of the lathe, it didn’t take long to remove unwanted material and then sand through to 320 grit. A crack developed on the collar but was stabilised and filled with superglue and sawdust.

The bowl was reversed onto the expanded scroll chuck, however it could just as easily be attached to a carrier (at a lesser cost) using heat sensitive glue. Masking tape was used to cover the fins, which are now spinning towards the tool rest. The tailstock centre was used for extra support. The base can be trimmed and a foot created, however I chose to remove it and carve fins right into the centre.

I left about 5–6mm of wood in the base, located its centre point and drew the remaining spiral lines. These were changed slightly as I carved, relying on my eye to determine visual balance—just be careful not to carve too far! Remember you need to retain more wood than usual when turning to allow for the carving. When finished, the form will be a little heaver than you’d usually expect. Going over the carved surface several times resulted in consistent flowing lines, depth of cut and texture. With tool work complete the form was burnt and wire-brushed, and then set aside to dry.

The cracked edges were re-burnt and the residue wire-brushed to soften them.

Plans can change

Left to dry in a warm environment, a crack developed in the top, posing the challenge of working with nature, transforming the crack into a design feature. The great thing about using the carved and burnt approach is you can use already cracked and blemished timber, disguising qualities otherwise seen as flaws, usually resulting in rejection. This piece had soft, pale sapwood and some rot which would otherwise destroy a perfectly turned and sanded bowl. And now it had a major crack!

I ended up burning the cracked edges and wire-brushing the residue to remove some of the sharpness. Previously finished areas on the collar were sanded again to remove excessive burn marks and blend the two surfaces, leaving the cracked edges softened and natural looking.

Further developments

I considered making a stand but decided this would lessen the piece’s tactile invitation. I have used similar carving and texturing techniques on sculptural forms and hollow vessels to extend their visual and tactile appeal.

First published in Australian Wood Review, issue 36.

Andrew Potocnik is a woodturner and teacher who lives in Melbourne, see www.andrewpotocnik.com