Q&A for How to Harden Modeling Clay

Because modeling clay is oil-based. If you put the clay in the oven it will melt and could start a fire.

The paint on the modeling clay will harden, but the structure will still be fragile to the touch.

You can't loosen any hardened clay. Either it's modeling clay, and it won't ever harden; or it's one of the other 3 types mentioned, and it isn't designed to be remoldable.

You can't over-bake polymer. It doesn't actually "bake," it cures. Once any portion of it gets to a cured state, it will stay that way as long as you can keep the temperature steady and below its burning point. To ensure the temperature is steady in the air around the clay, place aluminum foil over it or put it in an oven-proof container. You can even use a cardboard box if it will be sitting at least several inches from the heating element since the temperature should be below 300F (check manufacturer's instructions) and paper/cardboard burns at 451F.

You can't. But if you want, you can paint it and the paint will harden.

By the feeling of the clay. If it's super soft and smells toxic, it is salt based and is also known as play dough. If the clay feels plaster-ish (hard and pasty), this is likely to be polymerclay, and the last type is modeling clay, which feels soft and does not air dry.

Yes, but after a while after taking it out, it again becomes soft. It just temporarily becomes hard.

Yes, but if you put it in the freeze for a long time then take it out, it will become soft again.

It says that you can't do that or it'll melt.

Yes, as long as it’s below its burning point. You can also bake the details you would like to add separately, and then glue them on to the finished piece.

Yes. You should bake it. Otherwise it will stay soft and degrade.

Yes. Most, if not all, clay (with the exception of modeling clay) can be sealed/varnished/painted after curing.

It will not if the clay has hardened already, but if it wasn't hardened, it will be soft.

You can't with heat, it melts, but if you give it a thick coat of paint, it will harden the paint, and the clay will stay in form until you peel the paint off.

Put in on a baking sheet and put it on the middle rack of an oven. Bake for a while at around 300 degrees Fahrenheit. It can't be over-baked, so don't worry!

If you use a hair dryer on air dry clay, it will harden faster. Dehumidifiers in small chambers also help, but very little. Some people oven bake air dry clay, but that can be dangerous to your sculpt and cause bubbles or cracks.

Color changes while baking are often due to high temperatures scorching the outer edges of the clay. Try lowering the temperature {{convert|10|F|C}} and baking the clay for an extra 5-10 minutes.

Don't try this, you will likely break your toaster.

You can't if you want to harden it. Your best bet is acrylic paint left it to dry for about 24 hours.

Yes, but you can't freeze or bake play dough and will have to wait a month or so for it to air dry.

It is polymer clay, which is also oven-hardening clay as stated in this how-to.

Yes.

No, it will only slightly harden.

It's best to keep self hardening clay indoors where the temperature is consistent. Leaving the clay outside may cause the object to crack, due to wind or uneven temperatures.

You can't make modeling clay hard with heat, as it will melt. If you paint it, the paint should help to harden it once it dries.

No. Polymer clay is meant to be put in an oven to harden, while modeling clay is meant to never dry.

The best way to harden polymer clay is using a full-sized oven. A microwave oven or boiling water may cause the clay to break down and melt. If you don't have a full-sized oven available, you can use a toaster oven on the highest setting to bake polymer clay.

Don't put it in the freezer, or it will get too hard. Try a refrigerator and leave it in there for 15 to 25 minutes.

No, it will melt and you could potentially start a fire.

It takes around 1 hour to bake, but you should check on it every 15 minutes or so just to make sure it doesn't melt.