Where did you find this info Oldgit, it says nothing about it in the BAL Fixers Guide?
http://194.223.92.131/pdf/Technical Data Sheets/B & C Technical Data Sheets/Bal_White_Star.pdf
(1) Do not use shower for at least 2 weeks following completion of grouting - BS
5385: Part 4: 1992, clauses 6.3(f) and 6.4(h).
(2) Provided surface is sufficiently flat
(3) Check suitability of sheets/boards for the intended purpose with the
manufacturer.
(4) In frequently wet conditions tank out with the BAL-WP1 TANKING SYSTEM.
(5) The drying time will be extended in colder temperatures, when fixing to
impervious backgrounds or when fixing tiles of low porosity.
(6) Cured adhesive.
SURFACE CONSIDERATIONS
NEW CONCRETE/BRICK/BLOCK WALLING: Before
rendering/plastering/tiling allow walls to dry out by exposure to air for at
least 6 weeks. Direct fixing to brickwork or concrete may be carried out,
providing the surface is sufficiently flat. However, direct fixing to
blockwork is not recommended.
NEW CEMENT/SAND RENDERING: Before commencing tiling, allow
new rendering to dry out by exposure to air for at least 2 weeks or for
rendering based on BAL-QUICKSET CEMENT, 24 hours.
PLYWOOD/CHlPBOARD/FIBRE-RElNFORCED CEMENT SHEETS:
Sheets/boards must be dry, securely fixed and rigid, e.g. screwed to a
seasoned timber framework at 300mm centres vertically and horizontally.
Moisture resistant or exterior grade boards should be used. Seal the
reverse side and edges with BAL-BOND SBR to prevent distortion from
atmospheric changes. Do not seal or prime surfaces to be tiled. Check
suitability of sheets/boards for the intended application with the
manufacturer.
GYPSUM PLASTERBOARD BACKGROUNDS: Ensure that boards are
dry, securely fixed and rigid with no protruding fixings and the face
intended to receive the decorative finish is exposed.
NEW GYPSUM PLASTER: Before commencing tiling, ensure that the
plaster has been allowed to dry out by exposure to air for at least 4
weeks. Ensure that the finish coat has been applied and that the plaster
is free from dust, efflorescence and friable material. Cut back any
defective areas, including badly cracked plaster, to straight horizontal and
vertical edges. Thoroughly dry brush background and edges and make
good with plaster or a suitable non-shrinking filler. Plaster having a shiny,
polished surface should be thoroughly brushed with a stiff bristled brush,
followed by priming with a 1:4 BAL-BOND SBR:water mix or a 1:1 BALPRIME
APD:water mix. Allow the primer to dry.
FIBRE MESH REINFORCED CEMENT FACED TILE BACKER
BOARDS: Ensure that boards are dry, securely fixed and rigid and that
any fixings do not protrude. Do not seal or prime surfaces to be tiled.
GLAZED TILES/ BRICKS: Ensure that existing tiles/bricks are firmly
i wondered early on if id been priming for years without need,so i had a quick read.