EWJ FEB 59 2025 web - Flipbook - Page 41
Above, Low sodium area, the black pin mould is able to
colonise the areas marked in black on the picture.
Above, High sodium area, the black pin mould not able to
colonise the red areas marked on the picture.
The black pin mould colonisation is a reaction to the
availability of magnesium and calcium in the paint and
the gypsum that is evident on the walls, it is this that allows for the colonisation of black pin mould growth
once low levels of moisture, break down the Calcium
and magnesium and reduce the levels of sodium.
Calcium and reduce the sodium given the length of
time for saturation to wash the sodium out of the
plasterwork.
Field Observations and Hypotheses
Empirical studies indicate that:
High Sodium Zones:
Areas with significant efflorescence (indicative of high
sodium content) tend to show limited colonisation by
black pin mould in all the samples populations tested.
Indeed, a study by STEINBERG, R.A., AMERICAN
JOURNAL OF BOTANY 33: 210 (1946). It was noted
that Magnesium, calcium, and strontium increase dry
weight production in all the concentrations imposed
on samples. All the fungi tested have their vegetative
growth inhibited by sodium, the fungi tested had their
vegetative growth inhibited by sodium but the concentration causing inhibition can differ widely from
species to species.
Low Sodium Zones:
Regions where moisture saturation has leached
sodium away from the gypsum exhibit increased
mould proliferation in all the populations tested.
It is hypothesised that sustained moisture exposure
gradually depletes sodium levels, leaving behind an
environment enriched in calcium and magnesiumnutrients that promote black mould growth.
Indeed, it was found that even if salt solutions
(sodium) were imposed on samples, growth was still
obtained when high concentration of calcium sulphate
is delivered to the same samples.
These findings suggest that sodium content in
gypsum plaster is a critical determinant in the spatial
distribution of black pin mould within dwellings.
Therefore, Housing defects such as water penetration
actually, limit the ability of the mould to flourish in the
first instance, by extracting efflorescence from the gypsum, the reason why black pin mould is not seen
where efflorescence is in high concentrations.
(sodium)
Conclusion
In summary, the colonisation of dwellings by black pin
mould (Stachybotrys chartarum) is governed by a
complex interplay of factors:
This would indicate that sodium in the gypsum
plasterwork is a limiting factor for black pin mould
growth and the main reason why black pin mould is
not seen in areas of high efflorescence even when
saturated.
Material Composition:
The intrinsic properties of gypsum plaster and paint,
particularly regarding their chemical constituents, establish the baseline environment for mould growth.
It is hypothesised that the erosion of sodium from the
plasterwork through saturation would allow for increase in the levels of black pin mould found in properties given the saturation would leave high levels of
Environmental Conditions:
Moisture dynamics, such as water penetration and
subsequent efflorescence, modify the nutrient profile
by reducing sodium concentrations.
EXPERT WITNESS JOURNAL
39
F E B R UA RY 2 0 2 5
