This method is normally only needed on long, thickly matted and tangled hair, where a proprietary detangler or the conditioner method would not be effective.
Wear rubber gloves.
Fill a sink or large bowl with a gallon of very hot (not boiling) tap water and add to it a quarter of a cup of thick, unperfumed bleach from a new bottle of bleach.
Submerge the piece in this mixture and let it sit for about 2 minutes. You might see bubbles on the hair, this is the bleach working to detangle it.
Then take a wide toothed comb and comb through repeatedly until hair is very smooth.
Rinse it thoroughly.
Then place into a bowl of diluted shampoo in warm water and wash thoroughly.
Rinse well and condition with a good conditioner diluted in a bowl of warm water.
Rinse thoroughly again; dry and style as usual.
This method will eventually weaken the piece so is not recommended for regular treatment.
On the pieces I've worked on, the hair has been 18 inches long, colour #1B or # 2, Indian processed hair or Malaysian virgin (but permed) hair and who knows what else?
The hair, silk top cap and knots have not been affected by any colour change that I could see, either by colour leaching out in the water or after the pieces have dried.
I've asked Eric if I can post some pics to show how this makes a silk purse out of a sow's ear!