Your mission, should you choose...thoughts on fossilised Red

[Kim Strode]

With Bobs assistance I was able to get some thin slices of fossilised redgum from a small section I acquired some time ago. It has been been carbon dated at 40,000 years old and I want to use it for the back and sides of a Flat Top Mandolin. I realise it's not acoustically ideal, but I really like many aspects of it's 'quality'.

The question in my mind is wether to use it as is, leaving the fissures open and line the inside with a thin black timber veneer to seal the box, or fill the fissures with a glue or resin, combined with sawdust. If I attempt to fill the fissure or cracks, could I then sand the timber to the appropriate thickness, and or bend the sides and curve the back?

I would appreciate your collective wisdom.

[kiwigeo]

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[Allen]

I don't know Kim, but I'd be chomping at the bit to give it a go either way. I wouldn't get too heavily invested in time or money before I knew if it would bend though.

[Kim Strode]

...you crack me up Martin! Good suggestion Allen.. I'll try bending an off-cut first.

[Nick]

With all those fissures I'd be wondering about it's future stability, therefore a Resin fill would be a way to stabilize everything up.
If it bent ok then I'd give it a go as a back and side set. With heaps or resin in it it would be more of a reflective set rather than an active/live set.
Good luck with the build Kim and be sure to post pics

[Kim Strode]

I had considered resin, but I was concerned about wether I could sand the set to thickness, after a resin fill, and if the sides would bend with a resin fill?

[printer2]

Could always fill up your bending test piece to find out. Could always slice it thin and laminate another wood on the inside.

[curly]

Gday Kim ,
I've milled and dried a fair bit of ancient Red Gum . I'd be first to say that whilst it can polish out to the most beautiful silver black and we all love the story , it is also a complete prick to mill and dry (and work ). The essential structure of the timber is at least part way converted . I'd be fairly certain that it has taken up new minerals , likely silicates whilst having lost any solubles . God knows where the base cellulose /lignin structure has got to . It is one of the most reactive timbers that I have dried . One particular piece managed to twist a full 90' to a bowtie in drying .
I'd be inclined to sand the material out to a very thin face veneer which could be applied to a structural and tonally active body material . These would not need to be aesthetic or even necessarily matched . If you would like some falldown Blackwood ( just minor blemishes ) at no cost , then pm me . Given you are just down the road . There's also some more Ancient Gum trimmings if you need to bulk your lot out .
All the best .
Pete

[TimS]

Hi Kim,

One option you might liker to entertain is laminating the Red gum with carbon fibre cloth on the inside. After you have shaped the wood on the mould you could then laminate and glue the Red gum and the Carbon fibre. Having done this you could then "back fill" with resin from the outside without the drama of resin migrating through the carbon mat.

regards

Tim

[Allen]

Tim's idea may be a way of stabilising it too if it has a tendency to move about like Pete says.

[J.F. Custom]

Hi Kim.

I'd be suggesting you do the bend before any resin fill, at least, that's how I would approach it.

Make sure the side is well supported with a back strap covering the whole piece, for the entirety of the bend. With care, this should prevent fracturing along the cracks.

Then laminate it, if that's your approach and finally fill with resin in the regular finishing regime. I'd also just clear resin fill, as opposed to trying to use saw dust or pigment etc. I think that would best keep/enhance it's natural feature. But they are all my opinions only.

Good luck!

Jeremy.

[Kim Strode]

I completed the first stage in the testing phase by laminating a sheet of black maple veneer to the back of the fossilised redgum side and then sanding to 2mm thick. The side successfully bent to shape with the use of a heat blanket. The veneer seals the back of the side to openings and assisted in stabilising the red gum during bending.

I liked the suggestion of filling the fissures with a clear epoxy, but have limited experience with epoxies and are concerned the epoxy liquid would uncontrollably run down the curved side when poured in the cracks.

Can someone make a recommendation on the best epoxy to use, and can the epoxy be thickened to prevent it running away?

[Allen]

My concern with epoxy is that quite often it gases off during cure and causes bubbles to form in the resin itself. So if you are looking for clear, then you might have a bit of heart ache dealing with that.

If the intention is to see black, or at the least very dark voids that are level, then you could thicken with ebony dust, or even the dust from the red gum, which will turn darker with the wetting of the epoxy.

I use Bote Cote for inlays and thicken with ebony dust, or if they are very tight fitting just a few drops on color tone dye.

[Dennis Leahy]

My first thought is "kintsugi." Not necessarily gold, but something striking - like maybe copper or bronze powder, maybe even silver.

I definitely would not try to hide the cracks in any way. I think your technique of laminating a veneer to the inside surface is perfect: stabilizer, epoxy dam, and allows you to thin the Great-grandpa Red Gum a bit to help both with bending and again, stability.

Last time I spoke with the reps for "EcoPoxy" (epoxy made from soybean oil - no smell, non-toxic), he said that it would be available in Australia "soon." Might be worth an email to check how soon "soon" is.

Dennis