Post Curing

[Wdshea]

i am trying to do a tree with 5 rings on it, their cast weight all together would be about 25g in Argentium 935. all models are in B9 Yellow. plasticast with 3% boric acid.

i've been having constant casting issues as of late. i would probably think associated with the tree, since one offs aren't an issue.

my new burnout:
Preheated; 300*F 1hr
full ramp to 572*F hold 15min
full ramp to 750*F hold 1.5hr
full ramp to 1250*F hold 15min
full ramp to 1350*F hold 1hr
full ramp to 1100*F cast temp

my previous burnout didn't have the 300*F or 572*F, and were preheated to 750*F. 300*F was added thinking i need to dewax, 572*F i read is when all moisture should be removed from flask. 1250*F was to prevent overshoot and maybe remove anymore resin prior to 1350*F. i read investment can break down at high temps when carbon is present.

i flip my flasks ~15min before the 750*F is done. very good air flow to kiln.

the flasks look white when i take them out, cast under argon blanket. flasks are argon soaked in the kiln for 1hr before casting.

castings have inclusions (ash), some break down, and are brittle and break apart very easily. all castings come out the same regardless of burnout.

is the quantity of resin per flask too great? should i go ball to wall from room temp to 1400*F?

[Jewelermdt]

One nice thing about Microwaving is it's ready to invest in 30 min.

[Jewelermdt]

I would not think Boric Acid is needed with Plasticast. I use it to harden Satincast though sometimes.

I would also hold at 1350 for at least 2 hours if not more for that many models.

[Wdshea]

breaking out is difficult... the investment is like digging out drywall. i've done a few castings with just distilled and i couldn't believe it, so much easier.

[rkundla]

I'd agree with Jewelermdt, I don't think you are holding it at 1350°F long enough. What size flask? The bigger the flask, the longer the hold times to properly saturate the investment.

In an electric kiln using B9 Yellow and 2:1 Red/Cherry, I've been doing 300 - 1 hr, 700 - 2 hr, 1350 - 3 hr, cast temp - 1 hr at ramps of 1000°F/hr using a 2.0" diameter flask up to 3.5" tall and get excellent results in Sterlium+. I've stopped draining out the wax now and leave it button up the whole time. I can just program the kiln and come back in 7-8 hours ready to cast. Use Plasticast and the only water augment is 20g/l Calcium Nitrate to provide extra oxygen during ramp from 700 -> 1350 to assist burnout.

I'll be doing a gold cast soon, so I will see if this program is good for that as well.

[samatheang]

Some question please:
1) Why does some people add boric acid to PlastiCast? Does it help?
2) Are you guys using the same microwave for both food and curing the resin? Is it safe though? Just curious because one of my friend doesn't even want to put the investment binder in the same fridge with food. Lol

[M-Williams]

Usually Boric acid is added to satin investment .their is no need what so ever to add it to your plasticast. if anyone got some issues with plasticast .than they need to cure the resin more.If I have a big peace to cast i just lower a bit the water/powder ratio.You can use any microwave unit. Mine is 1200 W. A good curing is key.

[Wdshea]

i would agree with you about not needing the boric if it were true for me. i UV cure parts 8hrs, then heat cure up to an hour, and no matter what, i have to use the boric. i have no idea how anyone has success without it. i punched 12 3/8" holes in the bottom of my kiln and added powered ventilation and STILL i have issues without the boric.

yellow is a helluva lot better than cherry, but it is not an "ashless" resin.

do you vacuum your molds to remove ash?

[Archerm]

I have never used boric and have had 100% success. I now only cast all my resin prints in Plasticast. Full cure, longer flask bench set times, and faster temperature ramp up will give you the best results. Also I do not vacuum or blow out the flask before casting anymore.

[M-Williams]

You Have to keep it 1350 F for 2 hours. Not 1 Hour
You must have some fresh silver.never cast with scrap silver . it can also be the cause of failure.
Curing your prints is very important .