DIY investment making

[Derek Courtis]

Does anyone here have any experience making investment powder from separate ingredients?

I'm thinking of massively scaling up my current production level from individual pieces to casting big trees inside large flasks.
But I'm wanting to keep costs down as I go into it.
The commercial investment that I'm currently using costs $7 per kilogram.
And it looks like I can make it myself for as little as $3 per kilogram
[Note: these prices are AUD]
While $7 per kilogram is nothing when using tiny flasks, IMO that'll become a significant expense when doing large scale casting.
And when scaled up that's a massive potential saving to be had.

I had a quick look online and from what I can tell the basic receipe is 50% plaster with 10-50% silica.
Some people suggest to add something extra for refactory such as olivine sand or powdered fireclay.
In my case I'll probably also need to add some borax to prevent breakage during burnout since I'm using Senertek casting resin (which has a tendency to expand during burnout).

The way forward seems pretty clear...just have a go and see.
Only putting this out to the forum in case anyone has some experience or wisdom to share.

[Derek Courtis]

[quote="David" pid="279" dateline="1701318590"]
I don't but I'm very interested in learning about your experience.
[/quote]

I was afraid of that response....lol
Then in case I'll be sure to post my results up here after I get around to giving it a go.

[Javier Odom]

I have the same response.

However, your post has piqued my curiosity on the topic.

A quick look at this... (btw I am not going to trim weight figures)


Currency
When I ask Google what the USD to AUD is, it says 1 USD = 1.51 AUD.


RioGrande
Rio currently sells a 44 lbs bag of Ransom & Randolph® Plasticast® Investment for approximately $56.50 USD if you are buying one box.  Their site lists the best discount is if you purchase 24 or more boxes at $52.00 USD.

44 lbs / 2.2026 = 19.97639153727413 kg

56.60 USD * 1.51 = 85.47 AUD

85.47 AUD / 19.97639153727413 kg = 4.2785505 AUD per kilogram


SHIPPING
Does Rio ship to Australia?  Is shipping what significantly changes this (approximate cost of 2.72 AUD per kilogram)?


IF you bought bulk...
52.USD * 1.51 = 78.52 AUD

78.52 AUD / 19.97639153727413 kg = 3.93 AUD per kg

Shipping for (24 * 19.97639153727413 kg) 479.4333968945791 kg would probably cost a pretty penny, but I would guess you may be able to negotiate a lower shipping rate for this, which would drop that ~2.72 AUD per kg cost.

All of that, and you are still not at the $3 AUD per kg you want to be at.  However, how much are you paying for your $3 AUD per kg supplies, including shipping?  Still under $3 AUD?


Localized Options
I do not know how shipping costs work in Australia, but I did find a company that sells an investment for $61.60 AUD for a 25 kg bag.  I also do not know if this is even the correct investment.  I am looking for options here.  That is approximately 2.46 AUD per kg.  If shipping is more manageable for this, that may get you closer to your $3 AUD per kg target and you would have a smaller ecological footprint (not shipping 479.4333968945791 kg + plus the pallet(s) and bindings across the planet), and you would be supporting an Australian company.

This was for a single bag.  If you are doing a lot of casting, then you may be able to work out a better price with them.

https://www.cjservice.com.au/satin-cast-20-sc20-investment
(I do not know this company, I just found them in a +/-30 second google search for https://www.google.com/search?q=australian+jewelry+casting+investment.)


My Thoughts
I would find a better price from an external vendor than your $7 per kg first.  If the investment formula needs tweaking, I would check in with the manufacturer of the investment to see if they would be willing to make a new recipe.  If they would do that, it would help you and them as they could market the product to other jewelers.  This would allow you to focus on making jewelry.

If you cannot find a lower priced alternative and you still need to make investment, then let's see about making "open source jewelry casting investment"...


General Ingredients

• cristobalite
• gypsum
• silicas
• modifying agents

I have also seen the following ingredients listed by Richard D. Austin:

• cristobalite
• gypsum
• quartz
• wetting, defoaming, and reducing agents
• fibers

From where are you getting your recipe and instructions?

Also, are you vacuum casting or otherwise?


General Reading
This is quickly going to get into chemistry meets casting shop ... perhaps practical chemistry.

https://patents.google.com/patent/US6013125A/en

66th_annual_tech_conference_and_expo_book.pdf

This is going to be an interesting project!

[rosemary]

Yes please.  A casting investment recipe would be helpful!

[Javier Odom]

I am curious where you are in this project as well. If you want anyone to help you experiment let me know. I can set some time aside to try some different formulas and test them.

[rjt]

i've never made my own but I'v used investment someone else made for us.