Before taking this on, be aware that there is a fast shrinking process as well, so if you want to look into that and see if it interests you, please visit the shrinking preface page: http://www.dirili.com/mh/shrinkop.html
So, step by step:
Materials you will need:
Glass jars: I use 16oz 3.5"x3.5" ones that I got from Amazon (http://www.amazon.com/gp/product/B00KF5STQC/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1) It is VERY important that you use a jar that is large enough. 8oz 2.5x4" jars are NOT large enough and your head will crack at the thinner parts of the vinyl without enough room to expand.
100% Pure Acetone: I have been using ONYX Professionals 100% Pure Acetone Nail Polish Remover from Walmart and it seems to have been working well for me thus far.
Optional: Some sort of springy stuffing: I believe I use polyester stuffing. Test whatever you get with the acetone first to make sure that the acetone won't melt it inside the head. This is for keeping certain heads from warping as they shrink. Many head sculpts are thin particularly at the temples and some will start to cave in a bit, so when a certain amount of shrinking has occurred and the head is a little less fragile, it is a good idea to insert some stuffing in the upper part of the head to keep the temples from shrinking inward.
1. - Remove hair if you are going to reroot. This will also reduce the amount of acetone used getting soaked up in the hair.
2. - Wash the head. Just some dish washing liquid in tap water should suffice to get rid of any oils and grime. Make sure that the soap is completely rinsed out.
I just eyeball the ratio, but you can use a more scientific measure if you like. I fill a jar about 1/3rd of the way with water then fill the rest with acetone, making sure you leave enough room in the jar for the head to be immersed without the mixture spilling out. Stir it a bit.
Soak the head in the mixture for about 48 hours. The head may be somewhat fragile at this point when you go to remove it so try not to lift it out by the hair, try to get your fingers around the head to lift it out. It will take 48 hours or so for the acetone to evaporate. With slow shrinking, curing time is completely unpredictable for each head. You have to check and see how hardened the vinyl has become. It's a slow process, so just checking once every 12 hours or so should suffice. When the vinyl starts to stiffen up some, that signifies that it's ready for the next stage. Most of the shrinking that it's going to do will have been done by this point, so if you want to shrink it more, soak it again. I usually do 3 soaks. Once the head is completely dry, it's very very hard. I believe I had read that the acetone breaks down something called "plasticizer" or something like that in the vinyl, which is the ingredient that makes the head soft, thus the harder consistency once shrunk in this method.
Between each soak, it is a good idea to RINSE the hair just in case, to avoid things like what I mentioned a few paragraphs ago about that Venus doll I shrunk. Don't think it could hurt anything. I'd hold off on actually washing with anything like shampoo and such till after you're done your final soak, just to make absolutely sure there are no unanticipated chemical reactions.
Also beetween soaks, if the temples or other parts of the head are sinking in too much, that's where the stuffing comes in, put some of that in the head after it shrinks a bit, to keep the sculpt from caving in. Remember to take it out again before the next soak. This is not as likely to happen with the slow shrink method, but it may happen from time to time.
You CAN reuse the same solution several times, but the effectiveness depends on how much contaminated it has become. There is no way to really know this just by looking, but some good indications are discoloration and if you see a lot of sediment on the bottom of the jar. Neither of those factors necessarily means that the solution won't work well, but they MIGHT hint in that direction. Conversely, even if the solution is still crystal clear, for some reason it may not work as well as the first dunk anyway. Even if the solution has become contaminated and weakened, usually the worst thing that will happen is you won't get much shrinking out of the soak and you realize it and prep a new batch. The only thing I would definitely caution against reusing, is if you are shrinking a Venus McFlytrap head, I believe it is the glue from her flocking that mixes with the acetone and makes her hair hard and brittle if you don't rinse it out pretty much right away after removing her from the soak.
- Rerooting Can be started on as soon as the head no longer fragile. If you plan on not widening the neck hole so that the head is pretty much permanently on the body, you definitely have to reroot first if your doll needs a reroot.
- Widen the inner neck hole If you put the head on while it is still somewhat soft, you can squeeze it on just fine, however, it will be VERY difficult to get off again if you ever want to take it off again for any reason. So, you can take an Xacto knife or something similar and carve out that inner circle a bit more so that the head can be removed again without breaking the anchor or the neck itself. You can also use flush cutters to trim the wings and base of the anchor for easier manipulation as well. I like to do this even if not shrinking a doll because I've had anchors break on unmodified dolls before. Of course if you waited too long and the head hardened off the body, you'll have to do this anyway just to get it on. Even with the widening, it's still a good idea to use a hair dryer to warm and soften the vinyl some before you put the head on. Makes the process even easier and safter still. Do NOT open the neck hole all the way like in the picture below, or the head will just fall down as far as it can without the ledge to keep it up farther on the neck.
- Pressurized reshaping You can alter the shape of the head by compressing it any way that you can think of. I've been big into altering Ever After High doll heads, and they are super round, so I like to make them more oval and give them a more pointed chin. I also don't care for many of the chubby cheeked Monster High dolls, so I like to squeeze their cheeks while drying too lol. I like to use a mini-vise, rubber bands, small boxes and some sort of padding to make various arrangments. Makeup triangles make nice padding against any marks that pressure points could put on your doll and you can usually pick up a pack of them pretty cheap just about anywhere. You can get pretty inventive trying to arrange a setup for your doll's new head shape. Make sure to check back every 12 hours or so to make adjustments as the head is shrinking. If you don't check on it, you might find the head head tilted or something because of the extra space and you might end up with an uneven sculpt. So be careful!
Here's a few of my finished slow shrinks:
Lagoona in the center was slow shrunk, one on the left was fast:
If you have any questions, you can email me at firstname.lastname@example.org and please make sure you put something in the subject that won't make me think it's spam.