Red Gum: A Challenging and Rewarding Australian Timber
Red Gum is an iconic Australian tree species endemic to the Murray-Darling Basin. It has adapted to the region’s seasonal flooding, relying on regular spring flooding for germination. However, due to river regulation for irrigation, these floods have become less frequent, leading to widespread stress and mortality among Red Gum populations.
It is also a very difficult timber to work, and the difficulties start right at the beginning of the chain.
Harvesting
Due to their size and extraordinary weight, Red Gum is almost exclusively harvested where it grew using portable mills.
Drying
Red Gum is notoriously difficult to dry. It has 8-9% tangential movement as it dries, which is a rather extreme amount of movement that results in significant warping, checking, cracking, and splitting – what the industry refer to as “loss”.
Even when successfully and properly seasoned, Red Gum expands significantly with humidity changes throughout the year.
Despite these challenges, Red Gum is still a popular timber choice in Australia with consumers (and a very unpopular choice with makers…).
The Timber
Why is it so popular? Because it’s beautiful! I’ve worked with Red Gum that showed dense figure on literally every single millimetre of its surface. It is staggeringly beautiful, and I personally love the red and purple tones that it brings to modern houses which are usually little more than white boxes.
Working with Red Gum
Red Gum is an extremely dense wood on the world scale (although by Australian standards, fairly middling) at ~900kg/m3. But despite its weight and hardness, it isn’t a strong timber.
Short and interlocked grain make it friable when working; it’s unsuitable for structural use, and traditional joinery like tenons have an unfortunate habit of breaking off. The total failure of chair legs is a real concern!
Red Gum is a recalcitrant and disagreeable timber. It doesn’t respond well to cutting tools, and woe betide the maker who tries to chisel it. James Krenov’s enduring legacy is the foolish belief that cutting tools are superior to abrading tools, imparting the belief that planing is next to godliness and sanding is akin to marrying a cousin, and nowhere is this fallacy more evident than working Red Gum.
Rasps, files and sandpaper will create beautiful surfaces that polish like stone. Chisels will create chip out, and planes will leave tear-out. Even card scrapers do not leave a particularly nice surface.
Interestingly Red Gum responds well to spinning tools. A spindle moulder with a helical cutter can leave a surface that is almost finish ready, which would never be the case with timbers such as Blackwood. You can also cut against the grain, as long as the cutters are sharp, something which is unthinkable with a timber like Blackwood.
Unlike most timbers, the higher you go with sanding grits, the better the results with Red Gum. With most timbers you won’t see a discernable difference beyond P180. On my Red Gum dining tables I sand up to P2000 and beyond, and the surface just keeps improving.
The best finish for Red Gum – nay, the only finish worth considering – is oil. Most of the time I use a tung-oil applied with a burnishing technique or I’ll build up 5-6 layers of a hand rubbed Danish oil. Because of its extreme seasonal movement, Red Gum will crack any film finish, and it will very quickly become hideously ugly.
Veneering
It’s unusual to find Red Gum as a commercial veneer. Veneer millers look for logs free of defects, which is rare in Red Gum. That said, I’ve had some commercial Red Gum veneer and gotten good results with it.
However, this is unusual. Normally I cut my own bandsawn veneers, an arduous and time consuming process that is murder on my shoulders. But it’s worth the effort. I saw my own slices at 3-4mm thick for use in lumber core table tops.
The reasons for this are three-fold: for one, Red Gum’s high seasonal movement make it difficult to live with on the large, flat expanse of a table top. An average sized table top will expand as much as 10-12mm in Victoria, and even more in humid parts of the country. All this means that the large, flat expanse of a table top won’t be flat for long.
By sawing veneers and using Paulownia as the lumber core, the movement is all but eliminated, as the thin Red Gum veneers aren’t strong enough to overpower the Paulownia core.
Secondly it is a much more efficient use of Red Gum, which is becoming increasingly difficult to find.
Third and finally, a solid Red Gum 10-seater dining table is comically heavy. By using a lumbercore construction you get the beautiful Red Gum surfaces, without the weight penalty that comes with it.
Dealing with Cracks, Voids and Tear Out
Red Gum is full of cracks and voids, bark inclusions, gum veins and bore holes. Once I found a star picket embedded in a log that had grown around it.
Epoxy Resin
Liquid epoxy resin is my go-to for filling large voids and gum veins. I only use it dyed black, as the black colour is the least intrusive and rather than detract from the natural beauty of the timber, serves as a subtle backdrop to it. I use West Systems dyed with Japanese calligraphy ink.
Thin CA Glue
For borer holes that are already filled with dust, or areas of tear out created by cutting tools, the best thing I’ve found on Red Gum is thin CA glue (I use starbond because it’s what my local retailer carries, but I’m sure they’re all the same).
I put a few drops onto border backfill or sprinkle in some bandsaw dust to tear out and flood it with CA glue. This leaves an almost invisible repair on small areas.
Patching
If I need to fill or patch a larger area of damage, say some chip-out caused by some ambitious chiselling, I’ll borrow the stippling method commonly used in creative veneering. I take big-ish chunks of Red Gum mixed with smaller crushed pieces and some fine dust and fill the damage, using lots of CA glue or epoxy if it’s big enough. When sanded the irregularity created by the various sizes is less distracting than one large repair, which in Red Gum is always surrounded by a tell-tale black outline.
When repairing damage or defects, it’s important to bear in mind that the goal is not to create a perfect looking piece of flawless timber that looks like it was never damaged. The goal should be to reduce the obviousness of defects and damage, so it doesn’t catch your eye. If this isn’t possible, then you need to replace the part you’re repairing.
Is it worth the effort?
Despite how difficult it is to work, Red Gum is my favourite custom furniture timber. Its colour, figure and tactile nature are second to none.
Unique Characteristics and Challenges
- Drying: Drying red gum is notoriously difficult, with high loss rates and significant warping. Proper drying techniques, such as a combination of air drying and kiln drying, are essential.
- Movement: Red gum exhibits significant seasonal movement, requiring careful design and construction to accommodate changes in dimensions.
- Strength: While red gum is dense and hard, it is not particularly strong. Traditional mortise and tenons often fail, and dovetailing is all but impossible.
Working with Red Gum
- Tools: Red Gum responds better to abrasive tools than sharp edges. Belt sanders and spindle moulders are often preferred over hand tools.
- Sanding: Sanding is a crucial step in working with Red Gum. Multiple passes with finer grits are necessary to achieve a smooth finish, and the finer you go, the better the results will be.
- Finishing: Oil finishes, such as Organoil Hard Burnishing Oil, are well-suited for Red Gum. Avoid sprayed lacquers, as they will crack and peel due to the timber’s movement.
- Joinery: Red Gum does not compress at all. Unless your joinery is perfect, hammering a tenon into even a slightly too small mortise will crack a work piece. Floating tenons of a species such as Jarrah or even Pine are a more suitable joint for most applications.
Conclusion Red Gum is a challenging but rewarding timber that offers unique aesthetic qualities. By understanding its characteristics and working with appropriate techniques, craftspeople can create beautiful and durable pieces.