I remember reading on a beading forum that someone had managed to dye freshwater pearls themselves and had one of those "aha!" moments... I started to do a bit of detective work on the topic.
Most freshwater cultured pearls are colour treated; either by irradiation or dye. Irradiated pearls are normally greyish, the process darkening the pearl's nucleus which creates the deeper colour. Dyed pearls however are exactly that: coloured into may hues by commercial dyes. The process is almost identical to dyeing fabric. Dyed pearls can be identified by a higher concentration of colour in and around drill holes, and by the more saturated areas of colour where there are imperfections in the pearl's surface.
So- here is my diy tutorial complete with pictures:
1. Assemble your ingredients.
The pearls I started with were rice shaped, 3-4mm creamy white freshwater cultured pearls; the same as used below. Some have banding and other surface imperfections.
I bought two 50ml bottles of food colouring/food dye from my local supermarket in Rose Pink and Cochineal; (why did I not take more than one photo??)
To dye 6 strands of pearls I used about half or 25ml of each of these bottles. From memory they were about $1.60 Australian each.
2. Rinse pearls
Rinse pearls in a solution of dishwashing soap and hot water to remove any surface dust or grease. Give them a bit of a scrub; you don't need to be too delicate with them. I kept my pearls on the strand but I don't think this matters either way.
3. Make your Dye Soup
About.com's instructions call for a double boiler, but I used a small saucepan and got good results (but- be warned- I still have a pink-tinged saucepan despite lots of scrubbing!). Put the pearls in the pan and add water to cover. Add a splash of white vinegar (no less than a teaspoon. The vinegar acts as a setting agent- without it your colour will not be permanent).
Add food colouring or dye. This is a trial and error process- I found that a strong concentration of dye is necessary to get a dark pastel finish. This of course will vary depending on the type of dye you use. Stir the liquid and bring the contents of the pot to the boil.
You will see the pearls pick up the colour of the dye almost immediately. It's important to note that most of this colour will wash off; as a rule of thumb, the final colour will be half as strong as it looks at this stage. Note the spattering (but please, not the filthy stovetop- grimace)-- make sure you have a sponge or cloth handy.
4. Simmer the pearls at a low heat for half an hour. Make sure you are constantly moving the pearls around during this time so they don't singe- imagine you're making risotto! You'll need to keep topping up the liquid with water and dye as it evaporates. You won't see the colour of the pearls change much but the continual heat will intensify and set the final colour.
5. Remove the pearls from the water with tongs (or pass them through a stainless steel strainer) and immediately rinse with running water. Once the water runs clear, rinse again with dishwashing detergent and give the pearls a thorough scrub. I used a nylon dish washing brush for this. Again, don't be worried about using too much elbow grease here; you won't damage the pearls. Leave the pearls to dry in a sunny place on some absorbent paper towel.
6. Once dry, take the pearls off the strand and discard any that are noticeably banded or mottled. These rough areas are much more noticeable on darker dye jobs. Start with good quality pearls and you'll get a more consistent finish.
Contrast the picture above with these lighter pearls below, also home dyed using the same whitish pearls. The lighter shade shows fewer imperfections.
There is scope for lots of experimentation with this process; I've heard it works with faux pearls and I imagine you'd be able to dye mother of pearl too. There are lots of potential dye stuffs out there including specialist fabric dyes. I have a few vials of alcohol-based marker ink lying around that are begging to be used up. Then there are the natural dyes like saffron and tea and berries...
Make sure you leave me a comment if you give this a go. Happy dyeing!