In the following descriptions will use the general term
salt to represent any of the chemicals used, as the majority of them are indeed
classed as salts. To grow a crystal something called a Solution has to be made.
A solution is basically just a mixture of a number of substances, in this case,
water and salt. To begin with a solution known as a Saturated Solution has to
be made. From this a Super-Saturated Solution can then be created, this is then
used for growing the crystals, known simply as a Growing Solution. A seed crystal
is then planted in the growing solution and depending upon which method you
choose, either Evaporation or Sealed Jar, the crystal is left to grow.
Saturated Solution
A solution has to be made up which consists of a certain
amount of water containing a discrete amount of salt dissolved into it. If you
were to take a cup of water and stir in a teaspoon of salt, it would dissolve.
If you then take another teaspoon of salt and stir that in, it will also dissolve,
this process can be repeated for some time - up to a limit. The water can only
hold so much of the salt dissolved in it, after this no more can be held, the
excess sinks and settles on the bottom of the cup. Once this stage has been
reached the solution (water+salt) is said to be Saturated. A saturated solution
is vital if crystals are to be grown successfully. If the solution is not saturated
then a seed crystal placed into the solution would dissolve completely away,
which wouldn't make you happy. The reason is would dissolve is probably quite
obvious, if the water in the solution can hold a bit more salt, i.e you haven't
quite saturated it, and you place a crystal, which is really just more salt
in the solution then it will dissolve into the water until the water can hold
no more, as just described. So when making a saturated solution it is better
to put more salt in than needed rather than less, but saying that, it is really
a matter of experimentation as the amount of salt that can be dissolved in water
varies greatly with temperature as will be explained next.
Super Saturated Solution
As I've just explained, a certain amount of water can
only hold so much salt, but this is not strictly true, there is a way of forcing
the water to hold more, and this is done by simply heating the solution. There
are however exceptions to this rule. Table salt (Sodium Chloride) being one,
it doesn't matter if you heat or even cool a table salt/water solution the amount
that will dissolve remains the same
To make a Super-Saturated solution all that is needed is to heat the solution
and dissolve more salt in it. So for example we make a saturated solution and
find that after adding eight teaspoons of salt to an amount of water that it
is settling on the bottom of the jar being used, so we are pretty sure that
the solution is now saturated. If we take this solution and pour it into a saucepan
(Teflon coated is best as it won't react with the chemicals used) and very gently
heat the solution, we will find that we can add more salt to the solution and
it will dissolve, we add a bit more, that dissolves too, and as before when
making the saturated solution we can continue to add more salt, but again there
is a limit. Of course you could heat the solution to even higher temperatures
and this would enable you to dissolve even more salt in the solution, but for
the purposes of growing crystals this is not necessary, heating to temperatures
of a maximum of 100 degrees Celsius is more than adequate.
I said before that table salt is one of the exceptions to this rule, with table
salt you can make up a saturated solution but no amount of heating will allow
you to dissolve any more table salt after that. Most chemicals that belong to
the salt family dissolve in water and will allow you to dissolve more of the
salt when the temperature is raised, but there are a few exceptions.
Growing Seeds
In order to grow crystals you first need a seed crystal.
A seed crystal is really just a version, usually much smaller, of what the final
crystal will look like. Crystals made from different chemicals have different
shapes and belong to different system as they are known. But this is another
area and I won't go into it. But if you take a crystal made from Alum, at the
atomic scale the smallest crystal of Alum made from a number of Aluminium &
Potassium atoms bonded together by atomic forces in the shape of a cube. This
is the smallest seed possible, and is obviously no use to us. When you buy Alum
it usually comes as a powder. Just one grain of that powder can be called a
seed, remember though it is made up of millions and millions of atoms of Alum
and is huge compared to the original atomic seed, but even this is too small
for us to use. The best way to make seeds that are useful to us is, after making
a saturated solution we pour, say an ounce of it or more if you can spare, into
a small container, place a tissue or thin cloth over the container, to stop
dust settling, and leave it until all the water has evaporated away. What is
left is usually a few small crystals, they will vary in size but they will usually
be a few mm across or larger, and these are what are used in the next stage.
Two Methods for Growing. Crystals
There are two popular methods for growing
crystals from seeds. Both are pretty easy to do, but the Sealed Jar method requires
more care, having the advantage of growing the crystals more quickly.
Evaporation
Method
This is a very simple way of growing crystals, an advantage
being that all the salt that is not taken by the crystal to grow can be retrieved
and used again after all the water has evaporated. A disadvantage is that is
takes longer to get results.
To grow crystals by the evaporation method you don't
even need a seed crystal to get results. Find a piece of rock, light or dark,
it depends on the colour of the final crystal really. Next find a container
to grow the crystals in, a strong plastic one is best, but you could use glass,
it should have a large open top to allow the evaporation process to work, this
will be covered by a cloth or paper towel to stop dust spoiling the crystals.
The best thing to do is to place your chosen rocks into the container and fill
it up with water so it's 10-15mm or so from the top, just so that when you carry
it, it's not going to spill over the sides. Measure how much water this is so
you can calculate how much salt you will need to dissolve in it.
In all the following examples make sure that the growing
containers, jars, saucepan, etc are all clean. Best to wash them out in hot
water to remove any dirt or impurities.
Example 1
Say we filled the container as described and found that
it took 500g of water. Also we intend to grow crystals of Alum and referring
to the recipe, all you need is the [A] quantity,
which is 20g of Alum for every 100g of water, so we need 5 x 20 = 100g of Alum.
Measure out the 100g, best to use digital scales and pour it into your saucepan.
Next pour in the 500g of water and gently heat the solution stirring with a
Wooden Spoon or Stick don't use anything metal as it could react
or introduce impurities, keep stirring until all the Alum has dissolved and
leave to cool for 5-10 minutes. After it has cooled a while, pour the mixture
into the container so that it covers the rock(s). Then place a cloth or whatever
you've decided on to use over the top to keep the dust out. Put the container
in a place where it won't be disturbed and if possible where the temperature
doesn't vary too much. Leaving it for about a week should produce crystals of
reasonable size, 1cm or bigger. These will grow on the rock(s), and if you like
can be let pulled off to use as seeds. Alternatively you can leave them alone
for another week or two so that more crystals grow and get larger. Once all
the solution has evaporated take the rock out and dry it. You can pull off the
crystals to keep or use as seeds, or you can leave them if it looks attractive
and display it. If you choose to display the rock, it's best to keep it in a
container or some kind so that it doesn't get dusty, as trying to clean dust
off the crystals could eventually dislodge them.
Example 2
The example above describes how to grow crystals on
a base rock. This example describes how to grow large single crystals. You will
however need a seed crystal for this. For growing single crystals use something
like a jam jar or coffee jar as they are a nice size. The ones I use hold 200g
of water and this is sufficient to grow reasonable sized crystals. Measure how
much water yours hold first and then calculate how much salt you need using
the [A] quantity in the recipes. Once you've made
up the solution and it has cooled for a while pour it into your clean jar. Now
find a pencil and some fine thread, fishing line, sewing thread or invisible
thread and tie a slip knot around your chosen seed. This can be very very fiddly
especially if you choose a small seed; you will soon discover what is a convenient
size to use. Now this is very important, you must wait until the solution has
cooled down sufficiently before planting your seed, if you don't it could dissolve.
I wait until I can barely feel any warmth when I place the back of my hand against
the jar. Once at this stage, wind the other end of the thread around the pencil
and lower the crystal into the jar, adjust the length to try and get the crystal
hanging about 2cm or so above the bottom, then tape the thread on the pencil
to keep it in place. Cover this with a cloth like in the previous example and
leave alone for a week, again in a place where the temperature doesn't change
too much.. As the water evaporates the crystal will grow. Once the water level
has dropped below the bottom of the crystal then it won't grow any more and
you can remove it. It can of course be removed before this if you are happy
with the size. If you want an even bigger crystal, which most people do, then
make up another solution as before and re-plant your large crystal in it, it
may get so big that it will outgrow the jar eventually, and so you'll need a
bigger one and a larger quantity of solution.
Sealed Jar Method
Method This is the method you should
adopt if you want to grow large single crystals quickly. This method isn't that
much different to the methods described above. In this method the water dos
not evaporate as the container used is sealed, however, if you wanted to retrieve
the salt dissolved in the water you would have to leave it to evaporate. The
reason for the [B] quantity given in a number of the recipies will now becomes apparent. This method allows
you to grow crystals that are really big 3-4" or more in diameter, and once
started they grow an alarming rate.
Example
For this method you will need a suitable sized seed
crystal, a jar that has a tight fitting lid, some card and a length of fine
thread. Firstly turn you jar upside down and draw round its top rim with a pencil,
you can do as many as you like as they will come in useful in the future. Cut
out one of the circles and pierce a small hole in its centre. Next fill the
jar with hot water and put the top on it, this will warm the glass and lesson
the chance of it cracking when you pour the hot solution into it.
Stage 1
First of all you need to make up a saturated solution.
So again for the sake of argument we will use a jam jar that holds 200g of water.
You can of course use any sized jar or container you like that holds X amount
of water, all you need to do is then calculate the amount of salt required.
Assuming we use Alum then for 200g of water we need to dissolve 40g of Alum.
So as before you heat up the water and Alum, stirring until all the salt has
dissolved, as I've said previously you only need a gentle heat and so once all
the salt has dissolved you can turn off the heat. Now empty the hot water ouf
of your jar and shake it a little, the residual left won't matter. Now pour
all of the hot solution into the jar and screw the lid on. Leave this to cool
down until its barely hot. Then unscrew the lid and sprinkle just a pinch of
the salt (Alum in this case) into it. Replace the lid and screw it tight, then
shake the jar a little. Leave it for about 2-3 dsays, shaking it twice a day.
What you will see is that small crystals will grow at the bottom of the jar,
shaking helps the solution distribute itself.
Stage 2
After 2-3 days unscrew the lid and carefully pour off
the clear solution into your saucepan, try and pour off all the water leaving
behind the crystal sludge, as I call it, at the bottom. Scrape out all the crystal
sludge, and leave it on a saucer or whatever to dry, one it has dried all the
small crystals can be crushed back into powder and used again another time.
Now originally we used 200g of water and so checking the [B] quantity in the
recipe, we find that for Alum we need 4g per 100g
of water - so we need to measure out 8g. This we add to the clear solution already
in the saucepan and heat it gently as before until all the Alum has dissolved.
Wash out the jar with hot water, to clean and warm it. Then pour the hot solution
into it and screw the lid on. Now as the solution cools down the extra salt
that was just added remains dissolved in the water, this is now a super-saturated
solution and is our growing solution. While waiting for it to cool, the seed
can be prepared. Tie a slip knot around your chosen seed. Get the circle of
card you cut out earlier and push the other end of the thread through the small
hole in the centre so that the crystal is now dangling below the card. You will
need to adjust the length so that as before the crystal is about 2cm above the
bottom of the jar, once you've got the right length tape the thread on top of
the card to stop it moving, and cut off any excess. Once the solution has cooled
down so its barely warm, unscrew the lid and lower the crystal into the jar,
try and keep it in the centre so not touching the sides. The circle of card
will now sit on the top rim of the jar, and if you've got the length right the
crystal will be sitting 2cm or so above the bottom, if not then adjust the thread
and re-tape it. As the card circle is the same diameter as the jar rim you can
now just screw the lid back on, and the jar is sealed.. You can only use the
card a few times as it gets damp, which is why its best to cut out loads of
them. Now like before leave the jar alone and where the temperature doesn't
change much. Within a few days your seed will get larger, small crystals will
deposit at the bottom as before and some may grow on the thread. It is not desirable
that they grow above the crystal as small particles will drop down onto the
crystal and alter its natural shape. Before I plant the crystal I rinse the
thread and crystal under cold running water for a few seconds just to remove
any excess which seems to solve the problem.
Even Bigger Crystals.
After perhaps a week, it depends on how
much solution you make, the crystal will not grow any larger as all the excess
salt has been taken on by the crystal and seeds deposited on the bottom. If
you are happy with the size, then take the crystal out, dry it, and display
it or keep it safe somewhere. If you want an even bigger crystal then all you
need do is replenish the solution as described in STAGE 2. As mentioned before
if you keep doing this the crystal will eventually outgrow your jar and you'll
need a bigger jar and have to make a larger batch of solution, the new larger
solution would have to be made using the procedure given in STAGE 1..
There may be easier or quicker ways of
obtaining large crystals, but the methods I have described here work, but if
you discover any other methods I would be interested to hear of them.
