Introduction: Wood & Resin Triptych
A few years ago I was given a small live edge slab of huon pine. Unfortunately it was a little bit too small to turn into a coffee table (plus I already have one I made), and a little too thin to turn into turning blanks for the lathe.
Instead, I decided to make some wall art.
- Live edge slab
- Epoxy/Resin. You can use polyester but epoxy resins typically have a much more friendly mixing ratio - something like 2:1 compared to 100:1 of polyester.
There are "casting" resins which are typically clear and cheaper than "adhesive" epoxies. Look around. I used Barnes EpoxyCast.
- "Filler" - something to fill up the resin so you don't use so much of it. For me, I used gum nuts and gum leaves from the back yard, and my turning supply store sells banksia nuts/pods.
- Mixing cup(s)
- Mixing sticks
Alternative: You could just use a circular saw for this, there isn't any complex cuts, you may have more cleanup to do however
Alternative: Jigsaw, though if you're going with a circular saw for ripping you won't even need a jigsaw. Unless you have banksia nuts, then you'll want to slice them with a bandsaw.
- Random Orbit Sander
- Planer (thicknesser) & Jointer. These are sort of optional, but it depends on the condition of the slab you use. Alternative you can just use a router with a slab flattening jig.
Step 1: Prepare the Timber
You can see the size of the slab to start with. Not huge. While I could have used the weird fork-line end, ultimately it would cost me more thickness and a whole heap more epoxy.
I knocked those bits off with with a jigsaw, then went over to the bandsaw to rip the slab in half.
Alternatively, you could use a jigsaw or a circular saw to rip down the middle, just not a table saw (no square edge to do it safely against the fence). Using a circular saw would mean you wouldn't need a jointer or handplane to square up the cut edges.
If you do have a planer (thicknesser), get those two slab halves even and cleaned up. If you don't, a router slab flattening jig is the way to go.
Step 2: Prepare the 'filling'
If you've never seen banksia nuts, they're pretty huge. When they're exposed to the extreme heat of bush fire, the seed pods burst open, flinging seeds far away.
In its full size, a banksia nut isn't particularly pretty or easy to use. Using a bandsaw, you can fairly safely slice them up creating "slabs" of banksia nuts. These have very interesting textures.
The other fillings - leaves and smaller gum nuts - don't need any prep, other than removing any dirt and bugs.
Step 3: Prepare the Mold/form
Its all well and good to pour epoxy all over the place, but that is going to get messy very fast. Using a form made out of melamine is an inexpensive way to contain it.
I cut my base to the width I wanted plus 32mm (using 16mm melamine), and the length of the slabs plus about 40mm to give me a little bit of wriggle room.
Then cut strips to make up the sides, the same length, but a little bit wider than the slab is thick. This allows it to be used as rails for a router jig later and/or give you more leverage to remove the form if it gets stuck.
Using the slab sections themselves, I screwed the form around the slabs, nice and tight. I found it best to screw from the base into the sides, then the sides together. If you're not very careful, screwing the sides together first can move slight amounts as the screws tighten, causing hairline gaps for epoxy to leak out.
Before pouring the epoxy, for additional 'non-stickness', you can use mold release or (what I used) - pastewax.
Step 4: Make a Sticky Mess (pour the Epoxy)
Don your safety gear (gloves and ventilation at a minimum) and measure out and mix your resin. The product I used called for a 2:1 by weight or by volume, but every epoxy is different so read the instructions careful.
Use digital scales to be as accurate as possible. Flat bottomed graduated mixing cups work fantastic and while they're more expensive than a cheap disposable drinking cup, they are reusable - the epoxy will generally pop right off once cured.
The first pour of epoxy is to just keep everything stuck down - nuts and leaves don't have much weight to them so they'll float to the top if you pour it all in at once. For me, this worked out at about 200mL for the first pour.
Mix your epoxy for the manufacturers recommended time at a minimum. This is the most common cause for epoxy not setting correctly.
Place all your 'filler' (gum nuts, gum leaves, banksia nuts, whatever you like) and pour the epoxy over top of it, from at least 10cm distance. This helps pop any bubbles - casting epoxies are much less prone to bubbling compared to "adhesive" epoxies, but it can still happen. If it does, wave a butane torch over the area (don't linger!) and they should pop very quickly.
Get it somewhere warm - 25c is perfect (you don't want it too warm) and let it cure until its hard.
After that, I poured on more, almost to the top. Then after that coat was dry, I used a router slab flattening jig to expose the cross sections of the gumnuts and make them flush with the slab pieces.
Then, the final pour.
Step 5: Cleaning Up Your Act
Hopefully by now your epoxy will be slightly domed over the slabs, even a little bit on the slabs is just fine.
Dry sand with a random orbit sander through 80,120,180,240,320 grits, before I moved onto wet sanding.
Some sandpapers are suited to different materials - they'll all sand whatever, but some excel at certain things. I used SIA's 1950 discs and they were faster than Abranet for me, when dealing with epoxy. I'm sure there are others that work just as well, maybe even better, but this is what I have on hand.
Vacuum between each grit so you're sanding the work piece, not the dust.
Wet sanding can be done with automotive/wet-dry sandpapers. Wet the paper, sand the epoxy. Work through the grits - 600/800/1200 is a good combination.
You can use Micromesh instead of wet/dry sandpaper. Micromesh should still be wet sanded, but is very fine abrasive going up to 12,000 grit. Be aware that their "1200grit" is their own scale, and is actually closer to 400grit.
The higher the grit, the clearer the epoxy will appear. Once you've sanded as far as you're going to take it, there are a few different polishing compounds you can use - "Brasso" works pretty well (apply with a rag, then buff off), or plastic polishes (like microgloss) can really bring out the shine in the epoxy.
Step 6: Finishing Details
A triptych needs to be three parts otherwise its.. well, not a triptych! I used my table saw and crosscut sled to make the cuts. A circular saw (with a fine, sharp blade) would do the same job, just take longer to setup.
You may need to do some touching up of the sanding, particularly along the cut edges, but the majority of the sanding done as one slab makes it easier to keep it all even.
After you've got it resanded in any spots, your favourite finish to the triptych. As this is a wall piece, rather than a table top or "reach out and touch" piece, any finish is going to be durable enough. Blonde shellac is a good option if you want nice and quick drying.
I used "Zennith SureHook Picture Frame Rail" to mount it to the wall - simply screws onto the back, then the other half screws into the wall using just a PH2 screw driver (no drilling needed into plaster), and the two parts just slide together.