Decorative enduit over brickwork

[Chancer]

I want to make a feature of a chimney breast (if that is what it is called in English) in one of the loft type apartments I am fitting out.

The brickwork is just too naff to jolly up with pointing, having been reclaimed after the WW1 bombardment. What I have in mind is to use a grey chaux render with a troweled finish, dependant on how it looks I may perhaps wax it to give an effet bêton ciré, I am going to leave a section of the brickwork exposed in the form of a hublot, this I will point with grey mortar.

As I no longer have any bulk materials on site nor an area for mixing I decided to use bagged chaux based enduit de renovation with a chaux colorant, I have done lots of outside rendering with this both by trowel and hopper fed gun, on parpaing I applied it direct but on the brick walls I first did the recommended gobetis (sand and cement slurry) first coat.

I can't countenace spraying enduit or gobetis in the nearly finished apartment as there is too much to be damaged so I will be trowelling it on, my question is:

For an internal decorative finish do I really need the gobetis? I know I wouldnt need one for a sand and cement render but perhaps the chaux based ones dont rely on suction and need an uneven surface to key to and hence cannot be trowelled on?

[pachapapa]

It is easier to trowel on a chaux based mortar than a cement mortar; chaux grasse is often added to mortar to make it stick easier.

[Théière]

Chancer, a gobetis (spritz coat) is usually only required on backgrounds with poor suction, dense brick and concrete.  Providing you can wet down the surface to prevent it sucking the water out too quickly from the chaux enduit it should be fine IMO, is there any polymer in your pre bagged mix?

[pachapapa]

Make sure no goudron stains on brickwork, if there is it will bleed through unless sealed.

[Chancer]

Thank you people!

No goudron that I can see, it seems to be mainly soot and ash on the inside, I think that when each floor had a fireplace or fireplaces (there are 3 condits in the chimney) they must have used coal not wood.

I will report back on how I get on, if its half as good as PPP's work I will be delighted, as it will be the focal point of the room looking like a badgers ar5e will not be tolerated [;-)]

[pachapapa]

Gypsum/Plâtre mixes are worth consideration, used a lot in france, plenty of info on link below.

http://www.platre.com/platre/

Plus some inspired case studies on ancient plasters.

http://www.platre.com/platre/getCaseStudyFile?unid=ff8080811c1a290e011c1c516eef04a1&file=Platre.com%20-%20Working%20with%20archaeologists%20to%20countertype%20the%20old%20Dubai%20plaster.pdf

[Théière]

That looks similar to the Patrimone (with more colours) that I use for faux pierre.