I finally drug out my forge after a move and started beating on metal again.  While my son was working a long piece of stock, he dropped it and it broke part the the coating on the refractory.  I know I need to fix it, but my question is do I need to pull out all the coating and recoat the wool, or go back over the top of everything and just put enough coating over the damaged area that it is the same thickness as everywhere else?  Second question is does it mater if I put a different refractory coating over the top of the existing?  I don't think it would matter, but if they don't bond, I could see if flaking off.

Thanks for the wisdom in advance.

Do you know what kind of hard refractory your forge has now? Many if not most hard refractories don't bond to each other let alone different brands of refractory. If you have some of the original then go ahead and try patching it, you don't have anything to lose.

The hard refractory I use, "Kastolite 30" is made to patch furnaces and is an excellent propane forge refractory.

Forget about using "refractory" Cement, Mortars, etc. They are NOT intended to be in direct flame contact in a furnace let alone a propane forge.

Were I to have the forge I'd just buy enough biodegradable refractory blanket (The kind that fibers caught in your lungs can be dissolved without damaging you're lungs) to make two 1" layers, rigidize them and trowel 3/8" +/- thick layer of a good high alumina refractory over it for the flame face.

It's not that big a job but takes some time and more importantly patience and if you read the instructions in the gas forge section pr Iforge we'll be more than happy to answer questions, share tricks, etc.

Frosty The Lucky.

I purchased a Hell's Forge, so I think I got their brand of refractory.  I think they called it Hellcoat.  I am not sure what it actually was, and I would just buy that, but it looks like they have gone out of business.  (This is what I get for basing decisions on a TV show, but that is a different conversation.)

Do you think the Kastolite would bond to the "HELLCOAT 3billion" or whatever the marketing manager decided to call it?

There is still stuff up online about Hells Forge products. I took a brief look at their instruction video for applying their refractory and read a little about it. They kept calling it "refractory Cement" and it was a time that marketers were calling everything refractory cement so there's no telling if it is actually a flame face refractory or a cement.

Regardless I doubt any other refractory would bond to it in the forge, not even another coat of the Hell's Forge, Hell Coat. The video instructions showed it being mixed like tempera paint and brushed on. In my experience that is way too wet.

I don't even mix a kiln wash that thin and kiln wash is a final coating as a little final armor to protect the refractory and re-radiate more IR back into the forge and if you applied multiple coats almost guaranteed to flake off.

However, I have zero experience with Hell Coat and you are the first person I've seen post anything about their products in quite a while. Perhaps someone else on the forum knows something about them.

If I ran across one of the forges for cheap enough at a yard sale and picked it up, no matter how good it looked it'd completely reline it, the first thing that'd go, never to return is the firebrick floor. A piece of kiln shelf is the ONLY think I'd consider for a replaceable forge floor. Fire brick is just too much of a heat sink with almost no insulating capacity. A firebrick on the floor is a hold over from a time when flame face refractories just weren't that good and nobody insulated propane forges at all so they didn't hurt anything. 

The issue with applying Kastolite 30 is how dry it goes on and no matter how wet you make it it never gets plastic. I trowel in it then using a piece of flat bar stock tamp it in till smooth. I don't know how I'd pull that off in a flattened oval like a Hells Forge. 

On the up side Kastolite when dry and fired is concrete hard at 2,600f and having a calcite binder and alumina aggregate is pretty resistant to forge welding fluxes.

There is a lot written here about forge liners and replacing them in the "Forges 101" section of the Gas Forge section of Iforge. I've written directions on how to line a forge so many times I can't count and they're all in forges 101.

Frosty The Lucky.