Hey Suzzane!
I've done
loads of these. There are two ways to do them.
The first way is with the transfer papers. - They are
water decals. The t-shirt papers need to be ironed on .... not something you can do with soap.
The paper is printed on, then when it's dry, it's put into water, and the backing separates after a few minutes and you can slide it off onto the soap. It's a bit of a faff really, but looks nice.
The second way is with a transparency. It can only really be used with moulded soaps, not slices. The trick here is to print with a laser printer! Make sure you cut the pic smaller than your bar! Then, pour a bit of clear soap into your mould. Wait for a thin skin to form, spritz well, and place your picture down. Then, pour a thin layer of clear soap over the picture. This will make it look like it's floating in the soap. Then, pour the last layer of soap. This is best as an opaque layer, so that it shows the picture off. You can add a sprinkle of glitter before the opaque soap if you like. It's best to leave the very first layer unscented, so that there's no chance of discolouration.
The pros and cons:
The transparency way is easier, but if you're not careful, air bubbles get trapped under the picture. Not a good look.
Also, if the soap is used, the top layer can separate off, because there is only a little bit of soap holding the sides together.
The water decals are a faff, but, you can make the soap any colour you like. Also, you can use any soap - a bar, a slice - just so long as it fits.
The decal doesn't sit inside the soap - it's on the surface. That means that you can make up bars, and add the decal when it's needed. The transparency has to be done while you're making the soap in the mould.
But, because the decal is on the surface, it’s washed off far quicker than the transparency ….. but that has a tendency to splitting.
So there are pros and cons to both methods, and it’s really is up to you which way that you think would be best for you, and what materials you are able to source. Good luck.