interior efflouresence at newly cut brick walls

[mminlondon]

We cut openings in some solid brick walls in our ground floor flat and now have problems with efflouresence accumulating on the cut surfaces at all the openings. We have no dampness in the walls anywhere in the flat, and no rising damp. The efflouresence is appearing from ground level up to 1m high at the cut areas. Above 1m, there is no problem, the finish is fine. The cut walls were originally plastered and painted, but the plaster failed below 1m and the paint bubbled off.
The contractor returned and removed the plaster and applied a Sika product instead of plaster that was supposed to do the trick.. It did not, and the efflouresence is now just as bad as it was originally.
Another contractor informed me that the Sika product has very specific instructions, including waiting a day between two applications. It's possible the contractor didn't apply it as per instructions.
Can anyone tell me what's going on with these walls and what the remedy is?

Thank you!

 

[^woody^]

The walls were not bone dry, and once you cut them you gave a surface for moisture to evaporate. As this moisture has come to the [new] surface quicker it has either bought some salts with it, or caused the salts in the plaster to surface too.

Alternatively, the reveals are allowing moisture across from the outside, or causing local condensation due to a thermal bridge from the colder exterior

You need to leave the bare reveals exposed for a few weeks to allow them to dry naturally and stabilise, or more likely the salts are near the surface now so they should be sealed.

Proprietary products are effective if applied properly