The dog show

Jeff everything looks good. There is a hair line crack running across the switch cover. Why, I have no idea. That thing is too small and has way too much detail to even think about getting the tig machine near it. I'll pour the dogs soon. I've got a lot going on the next few days, but I'll try pal.

 

I wish man. Gotta fly the cowboy's game.

 

Jason, Just turn your machine down to 4 amps and use the foot pedal.

YOU CAN DO IT!!!

Gotta video the process though.

 

It's such a fine crack, I'm not touching it. I'll see what it looks like after I bead blast it. I would however try using the laser welder on it if I was in florida. Hopefully that machine wont get screwed over in the storm. They sandbagged the front door and of course some sack of shit stole the sandbags. Luckily, the duct tapes the lower 2 feet. Humanity has absolutely gone to shit these days.

They are using the iweld professional.

 

Looking at the pic i would say that the bronze has contracted when it cooled, had nowhere to go and caused a hot tear.
This could be because of either mould strength, uneven wax thickness/sprue placement.

(Mould strength) this tends to happen with ceramic shell more that block investment as it is stronger under compression than the plaster investments.
An exaggerated example of this is when casting hollow pieces (imagine a tube or a beaker) because the metal shrinks around the ceramic 'core' until one of them 'gives'. Usually the metal 'gives'!
I try to compensate for this by shelling the cores with the bare minimum of slurry dips so that it holds the metal while pouring but 'gives' when the bronze contracts while cooling. Its a balancing act that takes a bit of experience.

(Uneven wax thickness) im not sure how much wax thickness difference there is between the edge of your switch cover and the centre near the switch hole. If the centre is quite a bit thinner than the edge then the centre will cool and solidify while the edge is still hot and liquid. Then when the edge cools and contracts it is pushing against the already solid centre.
On top of this one you can also get a section near a pouring sprue that solidifies while the sprue is still liquid and the contracting cooling liquid sprue pulls the already solid metal, causing it to 'give'.

 

Im with OCD on this one!!! You can do it with a steady hand and a light touch. And if all else fails, you can be a grinding god!

 

Nice pours! I had a feeling it would all come out nicely.

I think the black costing can be from a few things, a pour that is too hot, and also if you coat your wax with slurry and then don't add the first sand stucco will also give you a black burnt looking surface.

I'm looking forwards to seeing the sand blasted version. Also your repair of the crack. Just throw a little boric acid over the crack after you sand blast it and hit it with a small OA torch tip #2 probably will do it. Or if you're feeling fancy your tig welder and let me know the settings you used because I have no idea how to tig weld bronze yet!!

 

John (Artopsy) brings up some really good points. One of the 6 sprues was actually cracked off the back of that light switch cover! So I got a tear there too. Just meant I didn't have to cut that one off. lol. Pouring this stuff definitily teaches one patience. The thickness across the piece isn't really that different, sure the center is thinner, but the hair line crack also runs through the thicker parts too. Why do I have a feeling I shelled too many layers on this cover? John is it safe to say, thin pieces, less layers and thicker pieces, more layers? I know, blanket statements are tricky when it comes to things with so many variables... hmmm

Zap, The darker pieces don't bother me and I didn't know that about slurry only on the first coat. None of these were dipped and allowed to dry without adding silica. Another head scratcher, so it must be a temp thing I suppose. I just had never seen pink and really brassy looking bronze. That one threw me for a loop. I still haven't sand blasted this stuff yet, had to work last night and now have to run back to an AC job. I'll try tonight to get into the blast cabinet and see whats what. I did get to knock off some tiny tiny balls on the rose and do a few minutes of cleanup. I'm going out on a limb here, but I believe teeny tiny balls on the surface are caused by an air bubble in the slurry. OCD came up with the idea of vacuuming the slurry. That would work, but the balls just pop right off with no ill effects. Just tossing that one out there.

 

As a general rule I would agree with you. I seem to apply less than the recommended thickness on smaller pieces. If im pouring a piece below a couple of kg with a sand support around the mould it is usually 3 slurry n sand and a top coat of slurry. I find the main problem with thin moulds isnt that they spring a leak when i pour, its that they hairline crack on burnout. I try and reduce this as much as possible with pressure relief holes drilled before burnout and patch it after but i still get cracks. I figure its just a part of the process now and ive never had a shell crack too much to be unusable. It doesnt take long to patch the hairline cracks, less than welding/fettling hot-tears anyways!

 

Yep, i think youre right. I sometimes get them in the deep recesses if ive brushed the first layer and not drained the excess slurry enough before stuccoing. I find i dont get as much if i gently air-line the slurry coating instead of brushing.

 

I used to do this with block investment moulds but havent tried it with shell casting. Even though its a small amount I didnt want it to contaminate my slurry. Id be interested if anyone has tried it how they got on?

Oh, i forgot to say Jason, nice job on the castings! You certainly are getting the hang of this bloody fast. Im seriously looking forward to the lantern project in bronze! Keep it up.

 

thanks John. Couldn't have done it without the help of all you guys. Onwards and upwards!

 

No question I'm adding air to the mix with the paddle.... I would guess having the stuff mixed properly is probably more important than a few teeny tiny balls. The switch cover had zero, the 2 mirror frames also came out clean. It's a non event really. I've been stuck up a wall today helping a friend out, but found time to fill a few small nasties on the backs of the mirror frames. Bronze welds like BUTTER. Don't judge the welding job, I was in a hurry as the mosquitos were carrying me away and I just wanted to put down some metal. The dogs are still stuck on the bench. :-(

 

I've been working on editing part 4 and I'm planning on pouring the dogs tomorrow. Here is a few shots of some work from yesterday. The odd colors of the frames had me a bit concerned at first, but after sending them through the blast cabinet, they are good to go. I bead blasted the rose and did the patina on it. I used HOT water and the smallest piece of liver of sulfur I had. I then took a torch and heated the bejezus out of the rose and started brushing on the liver stuff. Any thoughts on the patina? Patina is an art on it's own. Screw it up and you get black or it looks like some cheap brass piece of trash from pier one. I hope I pulled off the look without too much shine.









AC system is done. Waiting for a wall install before hanging the thermostat, but it's Ice cold in there now! That's 4 tons of cooling for under 4k installed. I like clean and mean installs.

 

sneak peak... lol and yes everything filled.