Ingredients:

white (clear) Vinegar
Sodium Thiosulphate (ingredient in most fish/pool products that are mean to remove chlorine from the water - I got mine at the pet isle of the grocery store)
Iodine tincture (check the pharmacy)
Liquid starch (I used a can of spray starch used in ironing)
Phenolphthalein (small bottle I gave you, can be ordered on-line, supposedly can use an extract of boiled red cabbage as well but I haven't tried it).
Basic water solution ( I found Austin tap water worked fine. However you might need to add something basic like baking soda or drain clog remover to make it more basic if solution doesn't turn red.)

Prep:

I didn't do exact measurements so here is my guess. Prepare before you start.

Liquid 1:
Vinegar (~1/2 cup) + spray starch (squirt for a couple of seconds) = clear liquid (our souls before sin)

Liquid 2:
Vinegar (good works)

Liquid 3:
Basic water + 1 good squirt of sodium thiosulphate (Christ is pure/sin free)

Presentation:

1. Explain Liquid 1 is clear/pure. Relate to the creation story and how this is the way we were meant to be and the way we were created by God.
2. Add 3-6 drops of iodine to Liquid 1 and mix to make a dark blue/black solution to represent what sin does to our souls, note that this sin separates us from God as he is pure/holy
3. Add some of Liquid 2 that shows we can do good works but our souls are still dirty and that good works will not make us pure before God
4. Show Liquid 3, talk about Christ, his purity as he was without sin, and his sacrifice. Add 4 or 5 drops of phenolphthalein to turn it to pink representing his blood and sacrifice on the cross.
5. Add Liquid 3 to Liquid 1 to make a clear solution while talking about if we accept Christ and He comes in it cleans our souls.
6. Add more drops of iodine to the newly cleaned mixture. Talk about even though we are pure before God, we still are not perfect and will sin. Note though as we add sin, the mixture is still pure/clean just as our souls are before God. Christ's sacrifice is sufficient for all sin (past/present/future)

-- RickMach - 17 Sep 2006