What is Alginate
Alginate is a natural polysaccharide compound derived from brown seaweed. Alginates are commonly used in various industries, including food, pharmaceuticals, and cosmetics, due to their unique gelling, thickening, and stabilizing properties.
Alginate is more commonly used in the production of dental impressions. In crafting, Alginate is popular for creating one-time-use molds for life casting hands and body parts.
This powder is safe for the skin, gentle, and even has a soothing minty scent and a cooling effect.
A good quality alginate will be able to replicate the pores, wrinkles and any marks on the body part up to the tiniest detail.
Stages of Color Changes
Alginate will harden fast and this is indicated by the color changes.
Once the light green powder is activated with water, the color will change to a deep pink paste. After a few minutes, this deep pink paste will change into a light pink and finally once hardened, it will turn to green. Watch the color changes to know how much pot life* you have left.
*Pot Life (Duration the paste can be stirred in the pot)
Here are the approximate working time depending on the size of the mold you are creating:
- Pot Life - 5 to 8 minutes
- Hardening time - 5 minutes
What you need
- A fresh high grade quality packet of Alginate
- Deep hand casting bucket
- Spatula Stirrer / Whisk
- Cool Water
- Weighing Scale
- Plaster of paris
On a general note, 500g should give you enough material to make a mold for one adult hand. If you would like to cast the hand up till mid-arm length, you will need around 1.5kg of alginate powder. To cast one adult foot, you may need at least 1kg of alginate powder.
TIP: Find a bucket that is narrow enough so you will need to use less alginate. The wider the container, the more alginate will need to be used.
How to use Alginate
1) Mix 1 part Alginate powder to 2 parts water. The powder will turn from light green to deep pink to indicate the mixture has been activated. See the color change in the photo above.
2) Stir hard and fast to remove any clumps as you add on more powder. If you find the paste too thick here, you can add a little more water until you achieve the consistency you desire. However you will need to work very fast as the Alginate will harden quickly.
TIP: To slow down the hardening rate of Alginate, use cool or cold water.
3) Once all the clumps are beaten down, dip the arm or body part into the pink alginate paste or pour it into the bucket with the hand submerged as shown in the photo below. There is a cooling sensation from the mint in this alginate.
TIP: Please remove all rings and bracelets so as not to damage the mold upon removal
4) Keep the fingers and arm still during this hardening process which should take about 5 to 8 minutes. You will notice the paste turn from deep pink to light pink and to green.
5) Once the alginate has turned to green, this indicates the mold is ready and the hand can be removed from the mold. Gently remove the hand, take care not to rip or tear the mold as Alginate can be fragile.
The ready mold will have a wet spongy bounce to it, this is normal.
6) Prepare your Plaster of Paris mixture by mixing 1 part water to 2 parts plaster. Stir well to remove clumps. Pour plaster mixture into the mold immediately and allow it to harden for at least 4 hours. 1 adult hand will need approximately 500g to 800g of Plaster of Paris.
TIP: Swirl the plaster around and tap the bucket to remove any bubbles that may be trapped inside.
7) Once plaster has hardened, tear the alginate mold to retrieve the hand casting. Alginate mold can only be used once and should be used immediately otherwise the water in the mold will evaporate causing the mold to shrink
Notice how true to life the hand casting is. A good quality Alginate will be able to capture every single line, hair, and skin fold to the exact model.
Other parts you can cast:
Imagine having a keepsake hand sculpture of your family or loved ones. And now you know how to make it on your own!
Extra Info: Alginate is also used in the cosmetics industry for its texture-enhancing properties in products like lotions and creams.