Lavastone beads are cool, but they become super-cool when combined with silver. They are really easy to embellish with precious metal clay (PMC), and it can be done without the need for any specialist equipment. This is an ideal project for using up tiny amounts of leftover PMC – it’s expensive stuff, you don’t want to waste it.

You will need

Several lavastone beads - black ones look best with silver and 16mm is a good size
A small quantity of silver precious metal clay (PMC)
Iron jewellers' binding wire (not essential)
A blowtorch (a culinary blowtorch is fine), a gas cooking hob or a camping stove
A wire mat, brick, ceramic tile, piece of terracotta flowerpot or other heat-proof surface
A pair of pliers or heavy duty tweezers
An oven glove (or something else that will allow you to hold hot things)
Olive oil
A clock with a second hand
A brass wire brush and an old toothbrush
Fine emery paper (or an emery board meant for manicures)
Safety glasses
Tiger tail, black leather cord or other bead-stringing cord/thread

Step 1: Preparing the Beads

Examine your lava beads. If they look jet black and shiny (like the ones on a string in the photo) rather than matt and dark grey, it’s because they’re coated in some sort of varnish/resin. This needs to be burnt off before applying the PMC.

Remove the beads you are going to use from the string on which they are sold. Do this one by one, placing one or two beads on a length of binding wire as you remove them from the cord - it's quite hard to find the right hole drilled through a bead otherwise, because of all the surface texture. Twist the ends of the wire together to make a loop that will allow you to handle the beads easily, and bend the wire a little so that the beads turn with it rather than spinning freely and sliding along the wire. If you don’t have any binding wire you will just have to handle the beads directly with pliers or tweezers when they are hot. (In that case, the best way to find the drilled hole again is to hold the bead up to the light and twist it around until you see daylight through it.)

Lay the lava beads on a brick or other heat-proof surface, or hang them up by their wire loop. Do this outside or in front of an open window because smoke and fumes will be generated. Alternatively, prop your beads on their wires over a burner on a gas cooking hob, but turn the extractor hood on.

Put on safety glasses in case the heat makes a bead shatter. Light the blowtorch (or gas hob) and play a not-too-hot flame over the beads until they stop smoking. Be careful because the resin finish may catch fire, and don’t breathe in the fumes. Turn the beads over (use pliers or tweezers) after a while and make sure the resin has burnt off the other side too.

Leave the beads to cool, which could take 10 minutes or longer. Don’t be tempted to drop them into cold water, they will probably shatter if you do and they need to be completely dry before you fire the PMC.

Step 2: Applying the Silver Clay

Rub a small amount of olive oil into your fingertips before handling the PMC. If it is a bit hard because it’s a while since you last used it, work a drop or two of water into it. If it's totally dried up, like the pale-coloured smear on the plastic film in the photo, more radical treatment is needed. But don't despair, that smear was enough for four beads. I crumpled the film over a pestle and mortar until all the dry flakes of PMC had fallen off, then crushed them into a fine powder. I tipped the powder into an egg cup and added tiny amounts of water, drop by drop, stirring well between each addition with a cocktail stick. Once the texture had become more clay-like, I oiled my fingers and worked the reconstituted PMC until it felt smooth and the right consistency.

Take a tiny piece of PMC – somewhere between the size of the head of a glass pin and a very small pea - and work it into a ball. It needs to be fairly soft. When it is, push it into the surface indentations on a bead, smearing it sideways as you do to make a random shape on the surface of the bead. Don’t push too hard into the bead, the PMC is expensive and you want as much silver as possible to be visible on the surface. You just need to push it in far enough for it to key into the surface, remembering that PMC shrinks as it's fired. Try not to leave any clay too proud of the surface though or it may look odd.

Repeat with one or two more pieces of clay of differing sizes on the same bead, then do the same with the rest of the beads. Vary the number, shape and placement of the clay splodges on each bead so that they don’t all look the same. Don't forget to wrap up any remaining PMC well to keep it in good condition for next time.

Leave the beads somewhere warm for a few hours until the clay is completely dry - you can speed the process up by using a hairdryer or a very cool oven. It is very important that there is no remaining moisture when you fire the PMC.

Once the beads have dried out, if there are any patches of clay you feel need a bit of smoothing then you can do that with emery paper or a fine file. It's easier to shape the clay than filing away the silver metal once the clay has been fired. Be gentle with the clay though, because it's brittle. It's easy to break it at this stage and have pieces of it fall out of the bead.

Step 3: Firing the Clay

Firing is best done indoors in a room that is not too brightly lit. You need to be able to see the clay glow orange and spot the telltale shimmer of molten silver. Have a clock with a second hand, or a stopwatch, to hand. Wear safety glasses because pieces of PMC could fly off if it isn't completely dry.

Place the beads back on the fireproof surface or wire them above the hob burner and, with safety glasses on, fire each one in turn - it's too difficult to get the timing right if you try to do several at once. If you have the beads on wires you will be able to hold them with pliers or tweezers (use an oven glove to keep your hand away from the heat), otherwise you may need to use something like a stainless steel skewer to roll a bead around as you fire it.

Check the instructions for the brand and type of PMC clay that you are using, but with blowtorch you will be firing small pieces like this for a much shorter time than is recommended when using a kiln. The timing that follows is suitable for Mitsubishi's PMC3 when using a butane blowtorch but may vary for other clays, and a longer time is likely to be required if the source of heat is a methane-fired gas cooking hob. Ideally, you need a stainless steel mesh to fire PMC on a gas hob, but it's not essential for small pieces. Use the biggest burner you have and position the bead immediately above a gas jet, not in the centre of the ring of jets - see photos.

Start with the heat turned low, playing the flame across the bead without directing it at any one place for too long. Aim to heat the whole bead evenly, not just the patches of PMC. The first thing you'll see is smoke as the binder in the clay burns away and it may look as if the bead itself is on fire. When the smoke stops, turn up the flame and keep heating.

Watch carefully to spot when the white-ish clay begins to glow bright orange and then time for 2-3 minutes more heating, depending on the size of the bead and the amount of PMC on it. You need to keep the orange glow without letting it become too much darker (which it will if the bead gets very hot), so move the bead nearer and further from the flame as necessary, at the same time as rotating it to heat it evenly. The lavastone bead itself may glow red, but don't worry about that - it came out of a volcano and no amount of heat is going to hurt it as long as it's dry.

If you suddenly see a spot in a clay area turn shiny, that's the silver melting and you'll need to move the flame away from that spot quickly or the molten silver will run down into the bead. This can happen with a blowtorch before the 2 minutes are up, because the quantities of PMC used are so small that it can easily overheat, but a gas hob isn't likely to produce enough heat to melt silver.

After firing all the beads, leave them to cool for at least 20 minutes before you try to touch them. (Again, best not to quench, the lavastone may shatter and even if it doesn't, you'll have to dry the beads out again if they should need re-firing.) The organic material in the clay will have burnt away to leave silver metal behind, but it will appear white at this stage, not shiny and metallic. You should be able to see evidence of shrinkage.

Step 4: Polishing the Silver

When you are sure the beads are cool, take each in turn and examine it. The areas to which PMC was applied should now have a white-ish appearance rather than the pale grey they were before firing, and you should be able to see where the PMC has shrunk away a little from the holes in the bead that it was pushed into.

If in doubt, brush a small area of applied PMC very gently with a brass wire brush or sand it lightly with fine emery paper. If it still seems brittle and clay-like rather than metallic, hasn't shrunk at all and doesn't become shiny when you brush it, then it hasn't been adequately fired and you will need to repeat the previous step, heating for longer this time. Otherwise, carry on brushing the surface of each bead until all the white-ish areas are silvery. Go over the beads with a nylon brush (eg an old toothbrush) after using the brass brush or emery paper, to give a gentle polish.

If you brush too vigorously you risk dislodging the silver from the bead, so be gentle. Keep working at each bead until the silver looks really shiny - this should only take a few minutes per bead.

Step 5: Making a Necklace

All that remains is to string the beads into a necklace. They look good on round black leather thonging separated by knots or on silver-coloured tiger-tail spaced out with crimp beads. If you don’t have many of the silver-embellished lava beads, then intersperse them with plain ones or with contrasting beads – rock crystal works well for a “fire and ice” necklace, and shiny silver-coloured beads make good partners too.