...Lifecast a limb using Alginate

This How-to will tell you how to make a lifecast of your hand or other limb using Alginate.

Alginate is a non-toxic, fast setting, water based moulding compound. It's main ingredients are seaweed and therefore is it safe to apply directly to your skin - it's the same stuff the dentist uses to make a cast of your teeth so that dentures and crowns can be made to fit.

The general process for lifecasting is to mix up Alginate with water, spread it on the area you want to cast, wait a few mins for it to set, pull it off and make a plaster cast from the impression. However, as Alginate comes as a powder and turns to liquid when mixed with water, you'll need to contain the whole thing inside something rigid so it doesn't run away, and it'll also need to be held firmly once it's set as it still remains flexible like a soft rubber. There are various methods to this, the two main ones are explained below:

Method one - quick and simple, but could be better

For this attempt we will simple mix up alginate inside an ice cream carton to contain it and stick a hand in to make the mould. For this we have used one large 550g pack of Alginate mixed with water to just over 1:1 by volume. This almost filled the ice cream carton:

After making sure the whole lot is properly mixed with water I stuck my hand in. You may wish to put a small amount of petroleum jelly such as Vaseline on any hair, although I didn't in this case and there weren't really any issues getting the Alginate off:

This Alginate is 'slow setting' which is around four minutes. It's important to try to get the Alginate to stick to every surface of your hand so wiggle your fingers around and generally try not to leave any gaps or air bubbles - this can be quite tricky using this this method as you can't really see what's going on.

After the Alginate has set, gently try to loosen each finger and move your hand around until you feel it release. Be careful not to tear the alginate as it's quite fragile. You should eventually be able to pull your hand out leaving a hole where it was:

You must use the Alginate mould as quickly as possible after making it. Alginate will quickly dry out, shrink and crack, so you only get one opportunity to do it right. Firstly fill the Alginate mould with water and pour it out into another container - this will rinse the mould out, but also you'll then know how much plaster you'll need to fill it. We have mixed up some Herculite 2 hard casting plaster and poured it into the mould:

After the plaster has had an hour or so to set, it's time to break it out of the mould. The Alginate will be fairly easy to pull away in chunks - if you use any tools etc to cut it, make sure you don't damage the plaster cast:

The piece has come out fairly well, although there are quite a few large air bubbles on top - this is where bubbles have risen out of the plaster and got trapped on the upper surface. If we turn the piece over there is also an issue where my hand was touching the bottom of the box - basically because it wasn't big enough. There are also a few lumps on the bottom where there was air trapped between the Alginate and my hand:

However, if we take a closer look at the cast, we can see some very fine detail has been picked up, which is what we wanted to happen all over:

We can improve on this method by spending an little extra time, and a small amount on extra materials.

Method two - almost perfect

This time, we will spread the Alginate onto the person, rather than putting the person into the Alginate. This will allow us to eliminate the air bubbles/gaps an also get an even thickness all over rather than having to find a box big enough - this way we can also make more effective use of the Alginate. We will use Modroc plaster of Paris bandages to hold the whole thing firmly once the Alginate has set so it keeps it's shape when it is removed from the person. You can use this method to cast other body parts as the Alginate can be spread onto any part of the body.

You may wish to put a small amount of petroleum jelly such as Vaseline on any hair, although I didn't in this case and there weren't really any issues getting the Alginate off:

Firstly we mixed up just less than one 550g packet of Alginate with water until it looked spreadable. This was probably more then one part water to one part Alginate, but we didn't bother to measure it:

The mixed Alginate was then spread all over my hand. You could attempt this on your own, although it's quite handy to have a helper. We didn't use all of the Alginate, so once you get the hang of it you'll probably be able to use about half of one 550g packet for this process:

The next step is to make a support case from modroc plaster bandages. We used around a few hundred grams of modroc for this. You'll note that it doesn't really set very well as the Alginate is full of water which stops it drying quickly. However, within 10-15 mins it should set rigid enough to support the Alginate:

Now it's time to remove your hand - try to loosen each finger and move your hand around until you feel it release. Be careful not to tear the alginate as it's quite fragile. You should eventually be able to pull your hand out leaving a hole where it was:

As before, we will make a plaster cast from the Alginate mould. You must use the Alginate mould as quickly as possible after making it. Alginate will quickly dry out, shrink and crack, so you only get one opportunity to do it right. Firstly fill the Alginate mould with water and pour it out into another container - this will rinse the mould out, but also you'll then know how much plaster you'll need to fill it.

We have mixed up some Herculite 2 hard casting plaster and poured it into the mould. However, this time we had opportunity to tilt the mould around which will coat the surfaces of the mould and eliminate most of the bubbles. As the mould is much easier to handle, it can also be left perfectly upright for the plaster to set, so any bubbles can rise to the surface instead of getting trapped on overhangs:

After the plaster has had an hour or so to set, it's time to break it out of the mould. The Alginate will be fairly easy to pull away in chunks - if you use any tools etc to cut it, make sure you don't damage the plaster cast:

The overall item is far better than the first attempt, although there appear to be two small bubbles in the underside of the fingers, the piece is highly detailed as before:

Important! - Remember:

Alginate is non-toxic - You can spread it on skin, although if you wish to use it to mould other items test a small sample first to check it doesn't stick.

Alginate is water based - It absorbs a lot of water so leave extra time for plaster casts to dry before removing them.

Try other methods - If you ware working with very young children or someone who won't stay still for long enough, try putting the alginate in a tray and making shallow impressions in it with hands etc. This way you can cast a 3D relief without struggling to remove body parts completely encased in Alginate.

Watch out for hair - it is possible to cast your face or complete head in Alginate, but watch out for eyebrows and eyelashes. Remember to cover hair and apply some petroleum jelly to any hair that may get stuck in the mould.

Make a reusable mould - Once you have the plaster cast, you can make more items the same by using it to produce a latex mould that can be used time and time again. Check out the main How-To index to read about latex mould making.