Which Hardener (H1 or H2) should I use?
The two versions of Newclay Hardener are used and act in different ways and you should use the one that gives you the results you require.  Hardener H1 is painted onto the model during or after drying and gives a case-hardening effect.  Hardener H2 is mixed into the Newclay and gives an all-through hardening effect. (If using Hardener H2 please note that the hardening process begins immediately and cannot be reversed, stopped or slowed.)

How many coats of Hardener H1 should I use?
Up to three or four coats may be required to give the desired surface hardness. It is unlikely that extra coats will result in additional hardening.

Do Newclay Hardeners (H1 and H2) work with other types of modelling clay? 
Newclay Hardeners (H1 and H2) have been formulated specifically for use with Newclay. They may work with other types of modelling clay, but the results are neither predictable nor guaranteed. We recommend you purchase Newclay for your modelling projects or experiment with the hardeners on unimportant pieces before using them on valuable models.