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Thursday, October 21, 2010

Bill Roll magic........

You will not impress anyone by
pulling out a bag or a roll of coins to
pay a bill. But you get instant
attention if you pull your dollar bills
off a thick roll!
You just need some currency that looks new, rubber cement ("the magician's friend!") and some pieces of paper that you cut to the same width as the money.
You start to assemble your roll of bills by gluing the edges of the pieces of ordinary paper with any glue that dries clear to make a continuous strip. You use these in the center so that your "money roll" looks fairly thick and more impressive.
Then you apply rubber cement to the very edge of your first note and press it against the end of your roll of paper pieces. Do this in turn with each note. Let the cement on each note dry completely before you put the next in place so that they do not all stick together in a lump when you roll them up.The rubber cement should ensure that you can remove the notes easily when you need to.

Scarf Juggling magic.........

This is real juggling but even the
clumsiest of us (that's me) can do it
in a fairly short time.
You need 3 colorful, thin nylon squares to start. Hold one in one hand and two in the other. Toss one of those two a couple of feet in the air and then toss the single square from your other hand directly across to the hand that launched the first square upward.
Now you catch the falling square with your empty hand.
Continue with this sequence for a few seconds, then try some variations or even add a fourth square to the mix. It is fairly easy to keep the squares jumping and to catch them because the squares float a little. You don't have to be as polished or nimble as the experienced jugglers who use balls, clubs and even axes.
Keep your routine short until you have worked out some variations that make it more entertaining for your audience. A short routine like this needs a surprise finish. One that works well is to have another square with a small high-bounce ball sewn into it. Make sure that this square matches the color of at least one of the regular squares you use in your routine.
To finish, gather the squares together in one hand, then pick out the one with the ball with your other hand and wipe your forehead with it. "Accidentally" drop the square and your audience will be surprised to see the square fall, but then bounce back up so that you can catch it!

Ball and Umbrella Juggling...

Ball and Umbrella Juggling
This is one of the
easiest ways to juggle
that you could find.
That's because it's "cod"
or false juggling.
You need to do a little practice so that you don't have to think what to do next and you don't do anything so obviously unreal that people know you have tricked them, even if they can't work out how.Find a medium-sized umbrella, a table tennis ball and some strong thread that is the same color as the cloth on your umbrella (a dark color is best). Tie and then glue one end of the thread to the point of the umbrella. Make a small hole in the table tennis ball. Push the loose end of the thread inside it and glue the thread in.
Show everyone the umbrella and the ball that you put carefully on top of the open umbrella near the center. The ball will not fall very far because of the thread but you do not let your audience suspect that the ball and umbrella are connected.
That's why you need to practice the routine in advance.
Use your other hand to spin the umbrella by its handle. You pretend that you are balancing the ball on the umbrella fabric as it spins. The thread gives you an advantage. You will, after some practice, be able to give a short, interesting routine that looks like really skillful juggling!

Tightrope Balancing Ball

Effect: A two or three-foot rope is held tightly between the performer’s hands. The performer proceeds to balance a ball on the rope and mystically the ball rolls from one end of the rope to the other.

Secret: A thin piece of black thread almost as long as the rope is used to build a track for the ball to roll on. Tie both ends of the thread near the ends of the rope leaving just a little slack. Facing the audience, hold the rope tight with both hands at opposite ends, the thread should be behind the rope. Insert your thumbs between the rope and the thread to spread them apart from each other, this is what creates the secret track. Now your ping-pong ball or hollow billiard ball can be rolled back and forth on a single piece of rope. This can be effectively used in a billiards routine or a rope routine.

The Runaway Knot..............

Effect: The performer takes a piece of rope and allows the spectator to cut it in two. The two ends of the rope are then tied together, and then held up. The magician slides the knot down the length of the rope, and makes it vanish. Secret: Take a three or four foot piece of rope and tie the ends together to form a loop. Start by holding the rope in your right hand, laying the knot of the loop across your face up palm. Take your left hand, palm face down, and place your hand into the backside of the loop and grab the other half of the rope with your left hand. Bring your hands together and lay the other piece of rope in your right hand, twisting your hands back to their natural position. This should cross the strings twice forming a small lock, immediately cover this lock with your right hand as you are bringing your hands together. Hold the rope with your left hand a few inches away from your right, and ask a spectator to cut the rope in between your hands. Covering the lock with your right hand still, it looks like two pieces of rope of the same size, hanging side by side. Now tie the two loose ends hanging from the top of your hand together without revealing the hidden lock, this knot can now be slid up and down the rope. Slide the knot off the rope to finish.

The Classic Rope Trick....

Effect: The performer cuts a rope into two equal pieces with a pair of scissors, and ties the ends back together with a small knot. The rope is quickly restored to its original state and the knot vanishes.Secret: This should be done with a three or four-foot rope, preferably a thin soft white rope. Hold the first end of the rope (A) under your thumb allowing the end to barely protrude in your left hand, palm facing you. Grab the other end of the rope (D) with your right hand and place it in between your first and second fingertips in your left hand. Place your right hand fingers under the bottom of the loop at the middle of the rope and bring it straight up to your left hand, lifting the rope with it. Just before you bring the loop up to your left palm, use your first finger and thumb to grab the rope behind your palm a half inch away from the first end (A). Bring this piece of rope through the big loop, and place the resulting smaller loop under your thumb between the two ends of the rope. Cut the fake loop making two new ends (B, C) and apparently two equal lengths of rope to the spectators. You actually have one real short piece on the left and one piece on the right almost the length of the original, both locked together by a loop behind your left hand. Drop both of the two ends of the longer  rope (B, D) on the right side of your hand nearest your fingertips, hold the ends of the short rope (A,B) keeping the secret loop still hidden with your left hand. Close the last three fingers of your left hand into a fist around the rope, and tie the ends of the shorter rope (A, B)together around the longer piece and drop one end. Holding one end of the rope now with your left hand, announce that you have restored the rope and wait for the laughs and haggling. Take the rope with your right hand, holding it by the knot, and wrap it around your left hand allowing the knot to slide off the rope as you do. If this step is done fairly fast no one will realize you are removing the fake knot. Reach into your pocket for some magic wizard dust, drop the fake knot into your pocket, and sprinkle the dust over the rope. Unwind the rope and hand it out for examination.

Color-Changing String

Effect: A white shoestring is held up for everyone to see, the magician passes his closed fist down the string, instantly changing it from white to black. The shoestring is then handed out for examination. Secret: Two shoelaces are used in this performance, a black shoestring and a hollow white shoelace. Cut a small opening in the white shoelace and thread the black shoestring through the hole, so that the black lace is completely covered by the white lace. Hold up the lace with your right hand covering the hole in the white lace. Using your left hand, slide the white lace down while holding the black string with your right hand. The black string can be glued into the white shoelace for convenience, but for a better effect don't glue it so that the white shoelace can be hidden and the black shoestring can be examined.

Tuesday, October 19, 2010

How to make easily black foam using chemical magic

Action:
TWO 200 ml. beakers are standing on the table. you pick BLACK CARBON them up, pour a clear liquid from one beaker into the other, which is one-tllirtf full of a white powder. Stir well with a stirring rod for a Fcw seconds aid then place the beaker on the table. Placing a white cal.dl)oat.d 1)ehind the beaker, the material begins to darkcn and  gives off fumes. In a few minutes a Black solid will rise several itlches above the beaker

You Need:
About 10ml. of conc sulfuric acid in the first beaker; 
powdered sugar in the second;
stirring rod.

Why:-
Black carbon remains wtren the sulfuric acid removcs the elements hydrogen and oxygen from sugar.cause the niaterial. to rise or Joarn.

Suggestion
For an instantaneous reaction, try the following experiment. From two 200 ml. beakers, pour two liquids simultaneously into an enipty 4800 ml. beaker. One contains 50 ml.concentrated sulfuric acid; the other is a concentrated sugar solution made by d i s s o l v i i~1~3 0 g r a n~so f sugar in 1~0 0m l.of water. Immediate reaction with considerable frothing occurs when the liquids come in contact. A large plate 01 paper should be under the beaker to catch the overflow the first metod produces sulfur dioxide fumes that are somewhat suffocating in a small ro0.m. The formalion of Black powder  gives the Demonstration a special appeal.

Magic to make Burning fire under Water

A MIXTURE of nitrate of potash, powdered charcoal, sulphur, and strontium nitrate driven into a strong paper case about two inches long, well closed at the end and varnished so as to be quite waterproof,may be set on fire and will continue to burn under water until the whole is consumed, provided that the cartridge be burnt mouth downwards (Fig.). The best effect is produced when burnt in a deep glass jar. 

Requirment:-
The combustible (red fire) is  made by mixing by weight:
strontium nitrate 40 parts,
flower of sulphur 13 parts,
chlorate of  potash 5 parts,
sulphuret of antl mony 4 parts.
Powder the ingredients separately, and then mix carefully on a sheet of paper with a paper knife. On no account must sulphur and chlorate of potash be rubbed together in a morta . being very liable to explode. The composition should not be kept for any length of time  before using, as is liable to spontaneous combustion.

Monday, October 18, 2010

magic of fluroscent writting...............

If a design be written or drawn on white paper, using a solution of sulphate of quinine as the ink, such design or writing when dry will be quite invisible. But if it be exposed in a dark room to the light of an ordinary Geissler tube or similar electric light the writing or design will appear in blue.

Similarly, if tungstate of calcium were used on a" brownish TIG. 8. or darkish paper, and the design exposed to the action of the X Rays (the X Ray bulb could itself be wrapped in black paper or placed in a cardboard or even a wooden box), it would appear in phosphorescent white.

If the (much dearer) chemical, barium platinocyanide be used, tne phosphorescence is much stronger and of a greenish tinge. It is with this chemical that X Ray
screens are. coated. Another chemical almost equally brilliant (phosphorescing blue) is potassium platinocyanide; it is also equally dear.

A magic of colour devoloper..........

Apparatus:-
A wooden frame (such as a slate or picture frame) on which is tightly stretched a piece of " unbleached " muslin. 

Chemicals:-
Sulphate of iron, nitrate of bismuth, sulphate of copper, prussiate of potash. Dissolve a small quantity of each of the chemicals in warm water. The first three named are your painting solutions, the last your " developer," as it were. Using a separate brush for each colour, paint 0K1 the muslin some (outlined) picture or design. It is not advisable to attempt much detail. Allow each colour to dry before painting the next. 

When dry all are quite invisible:-
To develop or bring out the picture all that is necessary is to spray on to the muslin a solution of prussiate of potash; the effect is hastened if the muslin is very slightly damp. When sprayed on with this chemical the sulphate of iron comes up blue, the nitrate of bismuth yellow, and the sulphate of copper brown. If the prepared frame be hung in such a manner that the developer can be sprayed on from behind without the knowledge of the audience the effect in a magical sense is much heightened. An ordinary scent spray or atomizer can be used, the sound being hidden by a little music.

How To Make Soap at home.....

The intention here is to provide the basic data on how to make soap from the most
basic materials. There are many fancier soap recipes which make better soaps, as
long as you have all the ingredients.
The first write-up assumes you can just go to a store and buy the ingredients. The
second only assumes you have some animals you will be butchering and that you have
been burning wood fires and cleverly saved the ashes.
Basic Method
[A. This first write-up is taken from Hulda Clark’s book, "The Cure for All Diseases,"
pages 529-530.]
A small plastic dishpan, about 10" x 12"
A glass or enamel 2-quart saucepan
1 can of lye (sodium hydroxide), 12 ounces
3 pounds of lard
Plastic gloves [really; use eye-protection too]
Water
1. Pour 3 cups of very cold water (refrigerate water overnight first) into the 2-quart
saucepan.
2. Slowly and carefully add the lye, a little bit at a time, stirring it with the a wooden or
plastic utensil. (Use plastic gloves for this; test them for holes first.) Do not breathe the
vapor or lean over the container or have children nearby. Above all _use no metal_.
The mixture will get very hot. In olden days, a sassafras branch was used to stir,
imparting a fragrance and insect deterrent for mosquitoes, lice, fleas and ticks.
3. Let cool at least one hour in a safe place. Meanwhile, the unwrapped lard should be
warming up to room temperature in the plastic dishpan.
4. Slowly and carefully, pour the lye solution into the dishpan with the lard. The lard will
melt. Mix thoroughly, at least 15 minutes, until it looks like thick pudding.
5. Let it set until the next morning, then cut it into bars. It will get harder after a few
days. Then package.
If you wish to make soap based on olive oil, use about 48 ounces. It may need to
harden for a week.
Liquid soap
Make chips from your home-made soap cake. Add enough hot water to dissolve. Add
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citric acid to balance the pH (7 to 8). If you do not, this soap may be too harsh for your
skin.
Basic Method When There Are No Stores!
[This write-up was taken from one done by Marietta Ellis concerning the soap-making
practices of colonial America, with the tense mainly changed from the past into the
present.]
Saponification is a very big chemical word for the rather complex but easy to create
soap making reaction. Saponification is what happens when a fatty acid meets an
alkali. When fats or oils, which contain fatty acids are mixed with a strong alkali, the
alkali first splits the fats or oils into their two major parts fatty acids and glycerin. After
this splitting of the fats or oils, the sodium or potassium part of the alkali joins with the
fatty acid part of the fat or oils. This combination is then the potassium or sodium salt
of the fatty acid. As we said at the start, this is soap.
Soap Making Takes Three Basic Steps
1.Making of the wood ash lye.
2.Rendering or cleaning the fats.
3.Mixing the fats and lye solution together and boiling the mixture to make the soap.
First Let's Make The Lye
In making soap the first ingredient required is a liquid solution of potash commonly
called lye.
The lye solution was obtained by placing wood ashes in a bottomless barrel set on a
stone slab with a groove and a lip carved in it. The stone in turn rested on a pile of
rocks. To prevent the ashes from getting in the solution a layer of straw and small
sticks was placed in the barrel then the ashes were put on top. The lye was produced
by slowly pouring water over the ashes until a brownish liquid oozed out the bottom of
the barrel. This solution of potash lye was collected by allowing it to flow into the
groove around the stone slab and drip down into a clay vessel at the lip of the groove.
Some colonists used an ash hopper for the making of lye instead of the barrel method.
The ash hopper, was kept in a shed to protect the ashes from being leached
unintentionally by a rain fall. Ashes were added periodically and water was poured
over at intervals to insure a continuous supply of lye. The lye dripped into a collecting
vessel located beneath the hopper.
[Use whatever you have available or can make.]
Now The Fats Are Prepared
The preparation of the fats or grease to be used in forming the soap is the next step.
How To Make Soap
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This consists of cleaning the fats and grease of all other impurities contained in them.
The cleaning of fats is called rendering and is the smelliest part of the soap making
operation. Animal fat, when removed from the animals during butchering, must be
rendered before soap of any satisfactory quality can be made from it. This rendering
removes all meat tissues that still remain in the fat sections. Fat obtained from cattle is
called tallow while fat obtained from pigs is called lard.
If soap is being made from grease saved from cooking fires, it is also rendered to
remove all impurities that have collected in it. The waste cooking grease being saved
over a period of time without the benefits of refrigeration usually become rancid, so
this cleaning step is very important to make the grease sweeter. It will result in a better
smelling soap. The soap made from rancid fats or grease will work just as well as
soap made from sweet and clean fats but not be as pleasant to have around and use.
To render, fats and waste cooking grease are placed in a large kettle and an equal
amount of water is added. Then the kettle is placed over the open fire outdoors. Soap
making is an outside activity. The smell from rendering the fats is too strong to wish in
anyone's house. The mixture of fats and water are boiled until all the fats have melted.
After a longer period of boiling to insure completion of melting the fats, the fire is
stopped and into the kettle is placed another amount of water about equal to the first
amount of water. The solution is allowed to cool down and left over night. By the next
day the fats have solidified and floated to the top forming a layer of clean fat. All the
impurities being not as light as the fat remain in water underneath the fat.
You may have observed this in your own kitchen. When a stew or casserole containing
meat has been put in the refrigerator, you could see the next day the same fat layer.
Finally The Soap Making Can Begin
In another large kettle or pot the fat is placed with the amount of lye solution
determined to be the correct amount. This is easier said than done. We will discuss it
more later. Then this pot is placed over a fire again outdoors and boiled. This mixture
is boiled until the soap is formed. This is determined when the mixture boils up into a
thick frothy mass, and a small amount placed on the tongue causes no noticeable
"bite". This boiling process could take up to six to eight hours depending on the
amount of the mixture and the strength of the lye.
Soft and Hard Soap
Soap made with wood ash lye does not make a hard soap but only a soft soap. When
the fire is put out and the soap mixture allowed to cool, the next day reveals a brown
jelly like substance that feels slippery to the touch, makes foam when mixed with
water, and cleans. This is the soft soap the colonists had done all their hard work to
produce. The soft soap is then poured into a wooden barrel and ladled out with a
wooden dipper when needed.
To make hard soap, common salt is thrown in at the end of the boiling. If this is done a
How To Make Soap
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hard cake of soap forms in a layer at the top of the pot. As common salt may be
expensive and hard to get, it is not usually wasted to make hard soap. Common salt is
more valuable to give to the livestock and the preserving of foods. Soft soap works
just as well as hard and for these reasons the colonists, making their own soap, did
not make hard soap bars.
In towns and cities where there were soap makers making soap for sale, the soap
could be converted to the hard soap by the addition of salt. As hard bars it will be
easier to store and transport. Hard bars produced by the soap maker were often
scented with oils such as lavender, wintergreen, or caraway and were sold as toilet
soap to persons living in the cities or towns.
Hard soap is not cut into small bars and wrapped as has been familiar. Soap made by
the soap makers is poured into large wooden frames and removed when cooled and
hard.
The amount of soap a customer wants can be cut from the large bar. Soap is sold
usually by the pound. Small wrapped bars were not available until the middle of the
19th century [nor maybe shortly after the end of the 20th].
Difficulties in Making Soap
The hardest part is in determining if the lye is of the correct strength, as we have said.
In order to learn this, the soap maker floats either a potato or an egg in the lye. If the
object floats with a specified amount of its surface above the lye solution, the lye is
declared fit for soap making. Most of the colonists felt that lye of the correct strength
would float a potato or an egg with an area the size of a modern quarter above the
surface. To make a weak lye stronger, the solution can either be boiled down more or
the lye solution can be poured through a new batch of ashes. To make a solution
weaker, water is added [more data to be added here on how to determine the correct
strength of lye].
A Pennsylvania Dutch recipe once carefully warned that a sassafras stick was the only
kind of implement suitable for stirring the mixture [see Hulda Clark comment above re
sassafras] and the stirring must be done always in the same direction [?].
Not Always Done Down On The Farm
Soap making as a trade had grown in direct proportion with the growth of the colonies.
Even in the very early days there were tradesmen making and selling soap, who were
called soapboilers. Since tallow was the main ingredient for both soap and candles,
many tradesmen were producers of both. These tradesmen were called chandlers.
Potash and Pearlash Trade
Soap making and the manufacture of potash and pearlashes were closely related
trades of colonial America. Pearlash, purified potash, because of its many industrial
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uses, was an important item of export for the colonies. Pearlash, in addition to soap
making, was used for making glass both in the colonies and in Europe....
Potash is the residue remaining after all the water has been driven off from the lye
solution obtained from the leaching of wood ashes. Pearlash is then made from the
potash by baking it in a kiln until all the carbon impurities were burned off. The fine,
white powder remaining was the Pearlash....

To turn Water to Milk and back again......very simple method

White fluids representing milk, etc., may be formed by
mixing soluble salts (in solution) with suitable agents, so
that the final result shall give a white precipitate in
suspension ; but the results differ much in appearance
and only a few salts are suitable. Soluble calcium salts,
as calcium chloride, are rendered insoluble, forming white
deposits with sulphates or carbonates, as sodium carbonate
or sodium sulphate. Soluble silver salts act in the same
way with chlorides, such as sodium chloride; as do also
the soluble salts of lead. Mercury salts and ammonia
give like results, and magnesium hydrate and sodium or
potassium hydroxide give heavv curdy precipitates
take one or two of the best:—
(1) To form a fluid resembling milk, mix strong
solutions of calcium carbonate and sodium carbonate;
to clear it, use hydrochloric acid.
(2) Use nitrate of silver and a saturated solution of
pure chloride of sodium; this is cleared by ammonia.
Avoid shaking, or the milk goes into curds at once.
The chloride of sodium must be pure—common salt is no
good.
(3) Sulphurous acid and acetate of lead, which is
cleared by strong nitric acid.

change IQUID COLOUR EFFECTS...Water to Ink, Ink to Port, Port to Water

Apparatus.—A decanter of about a pint capacity filled
(as before) with distilled water; seven wine-glasses alike
in shape.
Chemicals.—Tannin, perchloride of iron, oxalic acid.
About as much tannin as will lie on a sixpence is
dissolved in the distilled water in the decanter. Of
the glasses, numbers one and three are unprepared;
numbers two and four contain two drops of perchloride
of iron; number five about ten drops of a saturated
solution of oxalic acid ; number six the same quantity
liquid ammonia; and number seven a small tea-spoonful
of sulphuric acid. On pouring from the decanter, the
first glass (unprepared) gives clear water, the
gives ink, the tliird clear water, the fourth ink once
more (Fig. 1). The* contents of all four glasses are then
returned to the ^ decanter—the whole then appearing
as ink. The first four glasses are then filled from the
decanter, the contents still appearing as ink. A wave of
the magic wand over the fifth glass changes the ink
when poured in from the decanter to clear water, and
a wave in the reverse direction changes the same fluid
to port, or more strictly speaking to claret, in the case
of the sixth glass. The contents of all six glasses are
then emptied back into the decanter, the whole being
claret coloured. Once more six glasses are filled with
claret coloured liquid ; another wave of the wand or
suitable action as the performer fills glass seven
produces clear water once more.
The effect is much heightened if the glasses are not
arranged in a row but apparently haphazard, and
the final and semi-final changes not seemingly made
in any particular glass.
On no account should the contents be tasted.
v This experiment is one of many that can be performed
with quite ordinary chemicals, such as iron (salts),
tannic and gallic acids, salicylates, and such like
chemicals. By dissolving a few drops of ferric chloride
or perchloride of iron in water, the result is a colourless
liquid; but on introducing a few drops of a tannate or
gallate, the liquid is at once darkened, ferric gallate or
tannic galla*te being formed. To restore the liquid to
its original colour a suitable reagent must evidently
be used. Any acid which forms a colourless soluble
salt when added to the tannate would answer the purpose.
Oxalic acid is nearly always used, being the leastCHEMISTRY AND CHEMICAL MAGIC .
corrosive, easy to handle, and portable in a crystalline
form.
If we use a salicylate, such as sodium salicylate, in
place of a tannate, a beautiful purple colour is the
which can be reacted upon or cleared as before.

convert Wine in to Water

Apparatus.—Two claret (or wine) glasses and two
perfectly transparent decanters, one containing red wine
the other water.
Chemicals.—Permanganate of potash, pure sulphuric
acid, hyposulphite of soda.
If one gramme of permanganate of potash and two
grammes of sulphuric acid be dissolved in a quart of
(distilled) water a red liquid resembling wine is produced.
This liquid can be instantaneously decolourized by
pouring it into a glass containing a few drops of a
concentrated solution of hyposulphite of soda. A little
pinch of aniline dye, mixed into a paste with glycerine,
and stuck to the bottom of a second glass—(this device
permits of the gljiss being inverted or accidentally upset
without the contents being lost)—is sufficient to change
water to the colour of wine.
Decanter No. 1 contains clear water, decanter No. 2 the
permanganate and acid solution. One glass is unprepared
and one prepared as stated with the dye. The actual
presentation of any experiment will in general be left
to the taste of the reader. The usual method of procedure
in such cases as the above is as follows. One
of the guests or audience is asked to join the performer
in some refreshment. The guest is asked to select
one of the two decanters, and he will generally take the
one (»ntaining wine. On his pouring the contents into
the tumbler containing the hyposulphite of soda, it instantly
becomes colourless, and the water in the other
decanter is apparently turned into red wine on being
poured inte the second glass prepared with the aniline
dye. The glasses etc. should be immediately removed
on the conclusion of the experiment, owing to the turbid
appearance that the red liquid will assume after a few
minutes.
The mixtures are poisonous and must not on any
account be drunk.

Red-Black (Divide) Location

Red-Black (Divide) Location
I don't think I have to tell you that now you can count the cards of a
borrowed deck, do the deal jog to separate the reds and blacks, and then do
any of the standard selected-card locations utilizing the color separation.
Basically, have a card selected from one half of the hand-to-hand spread and
replaced into the other half, and so forth.
But here's a way to do this with which I've "taken in" magicians for years.
The idea has been ripped off a few times through the years, so it must be
good.
Assume you're in position-the cards are color separated (via The Great
Divide, or any other way). Have a card freely selected from the top half,
remembered-keep spreading-and have it replaced about a quarter of the way up from bottom. Square. It's all very clean.
Then, table the deck to riffle-shuffle position, cutting the lower half deck
to the left. Move back a bit so that you can comfortably see the long sides
of the cards, and start to legitimately riffle shuffle the halves into each
other. Just look at the long sides (of the left half particularly) and the
odd-colored card will stand out like the proverbial sore thumb!
(Particularly if you lift the cards of the left half a bit more than usual
as you shuffle.)
You don't need to know which color was, or is, where. It will be either a
red card among (near center of) the blacks, or a black card among the reds.
Either way, it will be hard to miss.
The thing to do is to "catch" that odd-colored index as you riffle shuffle
without pausing, without hesitation. Try it; you'll see that it's
easy to do. Remember the card, of course. Complete the shuffle. Then do one more riffle shuffle.
You've "broken" the red-black stack-the cards are really mixed- and you know the selected card. Let the spectator shuffle, and end however you like.
Afterthoughts: If you handle it so that there's no suspicion of a red-black
separation, this must fool!