Thread: My first attempt at butterfly keys over a cracked slab

Cheers guys - I'll give the shellac a go before I try anything else. A soldering iron is good for melting button shellac.

I've used West System epoxy with a few drops of Feast Watson Prooftint in the past, and it does seem to cure OK (although slightly translucent). Another option is artists pastels, which are available in just about any shade of brown you can think of. Just scrape the stick with a craft knife to get powdered pastel into your epoxy.

Thanks again everyone for your help.

I got bored with sanding and sanding, then more sanding so I did some research on the West System resins and it took me to this site

Epoxy by the Leading Epoxy Manufacturer | WEST SYSTEM Epoxy

So I selected the products I think I need and would like to run them by you before I fork out a small fortune, plus I've never used West Systems and have just learnt Exactly what and how resin works.

So basically I need to start with the 105 resin then add the hardener and any additives to achieve the desired result. These photos are the parts I think I need
(either the 406 or 403 filler additive, still not sure yet)

Forget the fillers if all you want is a bulk filler - they are for more technical purposes (such as boat building).

If it's just bulk to reduce the amount of epoxy you use, there are cheaper options (a bag of washed sand from Bunnies will set you back all of $10 after you factor in the sausage sandwich and a coffee as well...). Or flour, sawdust, router chips , coffee grounds, coffee beans or even the colouring material you want to use.

Mop unthickened stuff around the hole first to wet out the rough surface, then thicken the remaining epoxy with, say, sand, and glop it in. Wait for that to gell up and pour another layer. Did I say not too much in one mix? Not too much in one mix - read the hints and tips as you don't want a litre of epoxy boiling away like a kettle.

Mix your resin/hardener in measured amounts, not just 'looks like 5:1 to me!'.

And don't use sand in the final layer! (It's really hard to sand!)

As always, do some test pieces to work out what it'll look like. Colour wise, the colour when wet is what it'll be when it hardens.

now I'm thinking of a mix of iron oxide and aluminium for a table with an emergency destruct option....

Thermite work.

Mix your resin/hardener in measured amounts, not just 'looks like 5:1 to me!'.

This is absolutely important. A bit out either way, and you can finish up with a gluggy mess.

I have filled quite large voids 50 x 75 mm with melted button shellac without any prblems for the time I have had the pieces (a couple of years now). For smaller voids a soldering iron or a blow torch heated chisel (cheap Chinese variety chisel that is) works well. I keep my workshop clean so haven't ever had a fire with a butane torch (or any other cause), but clearly that is something to be very aware of as an atmosphere filled with wood dust, as well as bad for the lungs, could be explosive. I'll post some photos if I can find them, or take some more of wip.

Originally Posted by slidingdovetail

I don't own a gas torch so am wandering if melting shellac buttons on a stove or something will work?
I'm yet to learn about shellac, I've only seen the packet of buttons at the paint shop (is that the stuff?) it looks 'thick/clumpy' enough to use, plus AlexS has suggested it as well.

Hi Priscilla, Sorry for the delay in replying. Yes, the buttons are the type I was talking about. You can buy them in bulk from Shines Shellac supplies (0418 883 551) (Not my business - just a supplier I have purchased from some time ago). I think that melting them in a small saucepan or similar would work fine, though very hard to clean up afterwards unless you dissolve the residue with metho. My gas torch is a cheap butane replaceable cylinder model. I have included an image of a void in an unfinished raw red cedar board that I am filling with button shellac. It looks very dark now but once the cedar is fine sanded and polished it still looks darker but more like a dark knot. This one is 140 mm long by 30-45 mm wide (or so). The second, not very good example, is of a small filled knot in another, polished cedar board. The filler stands out much more prominently in a photograph than to the eye.
Regards

David

Shellac in unfinished board.JPG Small shellac filled knot.jpg

Good Morning Slidingdovetail

You have received a mixture of good and speculative advice above.

As you are a novice with epoxy I will start with the safety warning - read the safety instructions very carefully - it is nasty stuff and it has cumulative effects on the human body - one slowly builds up sensitivities to it. I get a slight twitch in my eyes when I smell wet epoxy, a friend has severe migrains for several days! Cured epoxy is virtually inert, IMHO. Double glove and heaps of ventillation and do not get any on any skin.

Usually I used WEST System or the local fibreglass shop's home brew (30% cheaper and indistinguishable). The resin and hardener must be measured accurately else it either will not cure or it will exotherm (go real hot, smoke, even catching fire) - WEST say maximum measuring error of 3%. Colloidal silica thickener cures to almost clear, the other powders mainly go very white (not translucent - I commonly use sanding dust for small holes & cracks as it blends with the wood, but it is very obvious with wider cracks. Then I prefer clear or black.

Epoxy hates moisture - it instantly goes cloud if you put it on a wet surface. And it will not cure properly at less than 10*C. Important issues in a Melbourne winter. Tricks include:

• dry and warm surface with a heat gun or hair dryer justr before applying epoxy,
• wet surface with MEK or acetone immediately before applying epoxy to aid penetration.
• lightly vibrate after epoxying to dislodge bubbles, if any.
• For larger holes, lots of thin layers, up to 3-4mm, rather than a single pour, to preclude exotherming.
• As soon as surface is not tacky, perhaps 2 hours, you can do next pour.
• Up to 24 hours epoxy forms chemical bond with previous coat, after 48 hours it is a mechanical bond. This is important with boat building.
• Do not attempt to surface sand epoxy until it is fully cured - surface will go cloudy. Could be 4-6 weeks in a Melbourne winter!
• If epoxy is too thick then just thin it with MEK or acetone.
• Once epoxy starts to go off, then an irreversible chemical reaction has started - adding thinners will not thin it!

Thin epoxy it an excellent varnish - very common on boats in spite of its hatred of UV. Just paint it onto your table like any other varnish and sand lightly between coats. I usually let the first coat sit ten minutes then rub it into the grain with an old sheet - a clear grain filler!

Danish oil goes well over the top of three coats of epoxy - often called faux french polish - and it is an excellent surface finish. Just rub on two or three coats of danish oil until you get the gloss effect that you want. Looks good and extremely durable - unlike french polish it is not suseptible to moderate heat or spilled alcohol.

In spite of the above, I actually like epoxy. It is an excellent product, but it must be handled properly; it is not very forgiving. I have had lots of failure - sorry, learning experiences. Best source of advice on epoxy are boat builders (including their sub-forum here) and the kids who build surf boards.

Finally, I would practice with all epoxy products before applying any to a real project. You need to assure yourself that this is the right product and you are using the right technique.



Fair Winds

Graeme

PS: Sorry for being so verbose.