First, I will assume you are talking about the exterior of the fireplace...and not the firebox.

How are you going to level the stone so you can adhere mosaics to it? A stone fireplace would be a very difficult surface for mosaic application.

Also, why do you want to paint before application? Installing tiles on paint is not a recommended technique.

I have refaced many fireplaces in my time and have typically installed marble or tile on them. I would recommend installing wonderboard over your stone so you get a flat and level surface to work on. Use both thinset and "screws" to attach your wonderboard. By screws I mean the proper drill bits and Tapcon screws than can penetrate stone or mortar joints. Most fireplaces are somewhat irregular and not 100% plumb...so you need to get that wonderboard vertically plumb by using the thinset heavier or thiner in problem areas.

If your stone is too much out of plumb, you will need to get that straightened out first. I would Tapcon wire mesh to the stone and then screed a mortar bed over the stone using boards installed vertically that are plumb as your screeding guides. You will need to use the correct mortar and mix ratios that will hold vertically.

Hi Pete thanks for your response.
You assumed correctly in that I am doing the surround and not the firebox..
I do not plan on leveling the surface. I am a mosaic artist and find the stone surface a real treat to be able to mosaic. As to the reasons for wanting to seal the fireplace first is because it has seen many a hardcore fire and the stone is still stained after many washings. I want to prevent any seepage of grease or oils still around. especially if I am going to do a direct application which is what I plan to do, in mixed media, mostly stained glass mosaic.
I have underpainted many a mosaic so I know it is and can be done in some if not most cases; just not sure about which sort of paint + clear adhesive could be used as far as the heat factor or if I should just use thinset.
I want to avoid thinset as I plan on grouting and I want a better control over the grouts depth ( I can be heavy handed w/ thinset )

Thanks for your advice on the squaring of the fireplace, I had battled with the thought earlier in my idea process but decided I'd enjoy the challenge of it's rustic surface to mosaic. But; if down the road I want it to disappear now I know how!!

Aren't you glad you're not married to me !! lol

Kathleen

Take and angle grinder to the stone and grind away the soot and stains to bare stone. Paint will not adhere to soot either.

It appears you are installing individually placed mosaics and not using sheet mounted mosaics?

Oozing up is always a pain !!!!!!!!

Several tricks...

I use white thin set and wipe clean joints as best I can as I install. I then follow up with white grout(..or grey thin set and grey grout if you choose). This is much more effective of reducing the very noticeable effects of colored grout over grey/white thinset that oozed out too far. I like white thin set and white grout the best.

One other suggestion...do a thick-bed set. Use a 100% solids epoxy for both your adhesive and your grout. Use 1/4" square notched trowel, then force the mosaics into the bed using a beating block and hammer. It is OK if the expoxy oozes up...just wipe the tile surface clean as you go along (scotch pads and sponges). When dry, use the same expoxy as your grout.

I still find it quite ambitious you are undertanking installation on an irregular surface. Depressions or high spots look very noticeable with mosaics, so they are usually installed on flat surfaces.

I don't know about cleaning soot on stone, but in my faux finishing business, I clean cabinetry (especially kitchen cabinets) with a solution of TSP to remove grease and grime before painting. It seems to work quite well, as my paints never show a sign of pulling away from the surface as I apply them. If your stone's not too porous, that might be a first step. After the stone has dried, you should be able to determine how well it worked by applying a few drops of water to the surface. If it beads up instead of merely running off, you still have cleaning to do. There are also products on the market that supposedly clean/remove soot, so you might check HD or Lowes for a bottle of that stuff too.

Yeah, I guess it is ambitious of me but I am not shy! This is a pic of the monster:

Thanks again for the tips, if I don't use them this time I certainly will at some point! I love picking other peoples brains when it comes to something new!

Kathleen

Hi Mike
thanks for the TSP suggestion, I did use that a long time ago to clean the stone.......... forgot all about it!

Kathleen

After seeing your picture...If I was doing this job..I would remove the stone veener face to the brick underneath. It appears you have a true masonary fireplace with brick behind the stone face. A lot of work regardless.

Thanks Pete!!

Oh I wish ..... Oh I wish it was a facade............... merely a veneer.......... :-( unfortunately it's whole stone, can't even call it field stone, ( hand picked and attractive ) more like what would have been ( might have been ) used for foundation stone in my old Victorian........freaking small boulders ........ rear side of fireplace is brick............. but, that's not the prob, it's in my laundry room .

I really appreciate the feedback from all!
Kathleen

Hi Kathleen, Good luck with your transformation. I do like your fireplace the way it is but I'm dying to see what your masterpiece is going to look like when done. Promise you'll post a pic for us?

I, too, think your fireplace is beautiful as is.

Elana, Susan;
Thanks for the nice words, I love having a wood 2 gas converted fireplace just this one leaves me flat. I know it ( mosaic ) will make the option of selling eventually possibly a bit tougher but I am pretty sure location will compensate for what might not be a future owners ummmmm taste, lol! OR, in an ideal world; my art work will actually increase the value of my house!!! ( ;0) )

Looks like I will have to put off doing it now until Jan. , I have an art show/sale this coming weekend and my annual holiday open house on the 17th and would hate to have my mosaic mess all over for the party! I promise I will post a pick when I start and keep y'all up2date! I am expecting it to be a long process.
Kathleen