14k Red Grain

[Eoghan]

I need to get my hands on some 14k red/rose gold casting grain. Cookson doesn't stock it, anyone know where I can get it?

[Dennis]

Not economical to import it, so best lower your sights and get 9ct red from Cookson. Dennis.

[enigma]

If its for a US customer I just tell them we have 9 or 18 to choose from.

[handmadeblanks]

I need to get my hands on some 14k red/rose gold casting grain. Cookson doesn't stock it, anyone know where I can get it?

Hi,

Cookson does 9k and 18k in RED so you should be able to mix the two to get 14k.

If I have done my maths right, for every 100g of 18K you need to add 80.288g of 9k

PurA + PurB = 0.375A + 0.750B

A = Weight of 9k
B = Weight of 18k
Pur = 14k/24 = 0.583

If you had 10g 18K then

0.583A + 0.583x10 = 0.375A + 0.750x10
0.583A - 1.67 = 0.375A
0.583A - 0.375A = 1.67
A = 1.67/0.208
A = 8.028g of 9k for every 10g of 18K


Just to check: (0.375 x 8.028 + 10 x 0.75)/ (8.028 + 10)

= 0.583 (14k)

It looks right...but it's late...and I'm tired

[handmadeblanks]

I looked at this again this morning and there is a slight rounding error. If you leave all the proportions as fractions the answer gives you 8 precisely.

So the ratio of 18k:9k to give you 14k is precisely 1:0.8 i.e. for every 1g of 18k you need to add 0.8g of 9k.

[enigma]

I forgot we had a mathematician on the forum
I think it can only be hallmarked as 9k though ?

[handmadeblanks]

I forgot we had a mathematician on the forum
I think it can only be hallmarked as 9k though ?

It's lucky you wrote this because I looked up the hallmarking law and 14K needs to be 585 not 583 as I calculated which means you can't make it with 9k and 18k alone...

[handmadeblanks]

Actually, I made a typo on my spreadsheet.

To get 14k (HALLMARKED QUALITY) @ 585

The Ratio of 18k:9K is 1:0.7857 ie for every 1g of 18k you add 0.7857g of 9k

It's been a long day...

P.S: I'd round down the 9k to 0.78g just to be safe or even 0.7

[enigma]

Thats interesting, I hadn't even noticed they offered a hallmark for that.
Good stuff.

[Eoghan]

Thanks for the help guys, interesting stuff. I think I'll offer the customer 10k or 18k for now. I'll definitely try experimenting with mixing 18k and 9k to get 14k for the future.