I am looking to make a small gas forge. All the articles on the internet are very helpfull, but they mostly specify American materials that are unavailable overhere. 

I am planning to use a ceramic blanket, valid up to 1260 degrees, about 2"think. Then coat that with a mortar like this one. Would that be good enough? What is this stuff really? Would it help to give it another coating with ICT-100 kind of material?

 

The Mortar has a higher thermal resistance than your blanket does.  However, how it will work with and adhere to the blanket is open to question.  It is intended to be gunned (spayed) on to solid surface or dipped to insulating brick. I hope someone with direct experience of the product can respond. Wam-2800 is more similar to Satanite mortar than the other.  Following the application of the mortar with and application of Ict-100 will make a better application.

Without  experience with the product this is all guess work on my part.  However,  more information may help  other better informed readers help you.  A design of your proposed application would help.

The design will be very simple. Just a round tube 10" diameter with 2" insulation. And a 3/4" venturi burner.

They also have a blanket for 1430 degrees but it is a lot more expendive. 

Higher temp if making Pattern welded Knives mostly.  Lower temp if only done occasionally

Kiln shelf for working bottom

 

Search around for ceramic (Pottery) supply.  What you want is kaolin clay (what porcelain is made from) and zircopax (made from zirconium).  Mix this together and coat the inside of your forge - somewhat tough and very reflective.  Ratio is 1:4 (clay to zircopax).  I've used colloidal silica (rigidizer) as the wetting ingredient with success.

Here's a start on your supply quest:

http://www.artsandcrafts.nl/webshop/?page_id=12

The mortar will work fine IF you use rigidizer on the ceramic blanket first. Most rigidizer is colloidal silica (better known as fumed silica), a light inexpensive product to have shipped through the mail; colloidal means it will stay suspended in water, which carries it well into the fiber blanket. Add a little food coloring and you can see how far it is penetrating. Let it dry and then fire it hard, before adding the no more than 1/4" thick layer of mortar. Yes, definitely paint the mortar with ITC-100; the fuel you save will pay for it in a few months.

Have fun and stay safe.