This might help lifted from BG website
HARDWALL:
"Thistle Hardwall is a gypsum undercoat plaster for use on
most masonry. With a final coat of Thistle Multi-Finish or
Thistle Plaster Finish it provides a smooth, inert, high quality
surface to internal walls. The combination has superior
impact resistance, earlier surface drying, a higher than
normal resistance to efflorescence, and gives a durable base
for the application of decorative finishes."
Table 1 - Thistle Hardwall range
PERFORMANCE
Common brick walls and concrete bricks (with raked joints).
Engineering bricks (with raked joints).
Dense aggregate and lightweight aggregate concrete blocks.
Aerated concrete blocks (pre-treatment may be necessary to control high
suction).
No-fines concrete.
BONDING:
"Thistle Bonding Coat is a gypsum undercoat plaster for use
on low suction backgrounds, e.g. some brickwork,
blockwork or concrete, Gyproc plasterboard, expanded
metal lath, or surfaces treated with bonding agents. With a
final coat of Thistle Plaster Finish or Thistle Multi-Finish,
Thistle Bonding Coat provides a smooth, inert, high quality
surface to internal walls and ceilings, and a durable base for
the application of decorative finishes."
Engineering bricks (with raked joints).
Dense aggregate concrete blocks and No-fines concrete.
Normal ballast concrete walls.
Normal ballast concrete soffits.
Other aggregates concrete.
Pre-cast concrete units/Composite ceilings.
Extended metal lath.
Backgrounds treated with
proprietry bonding agents
(e.g. glazed or painted surfaces).
Expanded polystyrene soffits.
Expanded polystyrene walls.
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