I'm Christian - a austrian certified master goldsmith.
I work since 2010 in a company that was foundet in 1762.
We have time to solve problems, and try some other ways.
I had a lot of troubles with the emerald , and other resins.
Now we cast with nerly 100% of sucess.
Here is our burnut and steps how to do it. AND YES we USE boric acid. - give it a try !
The most important thing:
good airflow out of the oven:
we use a oven with catalyst.
1) Rinse in Alcohol ( isopropanol 99 )
2) put the glass with alcohol and the models in the ultrasonic cleaner ( 1 Minute )
3) Rinse in Water. After that step blas it off with an steam blaster.
4) USE microwave ( important for emerald) = models in distilled water and 3 times for 3 minute in the microwave at 750W. let the water cool down a bit between.
5) Cure the models for half 1 HOUR in UV light. ( we use a light frosted plasic bottle - you only have to put it out of the microwave and put it in the UV light. )
Make sure, that before putting the models in the destilled water, that there are no small bits of resin in the water - they will stick to the new models.
Use Plasticast 38/100 and invest with distilled water. ( with 2% of BORIC ACID in the investment water = 5 litre 100 gr. of boric acid ).
let the flask rest a minimum of 4 hours after investing, before heating up !!!!
Ramp up to 100 C° ( 2C°/min. ) - hold for 1h30m. - hardens the investment.
Ramp up to 170 C° ( 2C°/min. ) - hold for 1h30m. - hardens the investment even more - after that time no water will be left in the investment.
Ramp up to 430 C° ( 9C°/min. ) - hold for 3h. At this stage the resin starts to bubble our of the investment.
Ramp up to 800 C° ( 9C°/min. ) - hold for 3h - 5 hours ( we use now 3 hours ) - At this stage - if there is resin left in the investment it will turn into ash. you don't get rid of it - you can't "burn them out".
Down to castin temperature ( 500 °C 18 KT whitegold and 550 - 600 for yellowgold - yes sounds strange, but we have a palldium whitegold with more than 15 % of palldium in it. higher flask temperature causes ugly surface.
AND - after casting let the flask cool down for 2 Minutes ant put it in a Bottle full of water. If the investment doesn't came out itself - some hammerblows with an old hammer on the flask and the thing is done.
Good luck and please tell me if it worked
There are so many "Experts" outside. Do not skip a step, write down everything, make phots.
A lot of problems are caused of carless upwaxing on the tree. make sure you have no sharp corners, fill up holes if needed. everything has to be smooth! And what we tried 1 year ago - and i think it was also written don in the santafe text.
If you want print letters, and models, that won't come out perfect - Print the piece, clean it, blas it of with a hot steam blaster and put it in a plastic bag ( airsafe ) and put it in the drawer.
After 3 weeks the pice has reduced its inner tansion/ stress. no curing. just bulidng up and casting.
The biggest problem is her the time!!!
Last 3 months we had never problems with our casting mehtod especcialy beacue of the boric acid!
We cast 200 to 400 gr. a week. This is our way to do it.
Here is a picture of our last casting
And! we had worse results using the recommended burnout from B9.