- To
Fight Micro-organisms in Ceramics
- (English
version by E. Bastarache)
-
-
- A
rapid survey of micro-organisms
:
-
- Micro-organisms
may vary in size from some nanometers (1nm =
10-9 meter) to several hundreds of
micrometers (1µm = 10-6 meter).
-
|
|
Types
|
Size
|
|
Viruses
|
10
to 300 nm
|
|
Bacteria
|
1
to 10 µ
|
|
Family
of Fungi
|
Yeasts
|
2
to 12 µ
|
|
Fungi
|
2
µ to x cm
|
|
Molds
|
2
µ to x cm
|
|
Lichens
|
2
µ to x cm
|
|
-
|
Algae
|
1
µ to x cm
|
|
Protozoa
|
2
to 200 µ
|
-
- Micro-organisms
are present everywhere in our environment :
-
-
- in
air, water, on surfaces, and on individuals of all
kinds. They are invisible and relatively unperceived.
Micro-organisms are very numerous: 1 gram of earth may
contain up to 25 billions micro-organisms (4 times the
population of our planet).
-
- Conditions
for the development of micro-organisms in ceramics
products are related to the presence of nutritive
elements under the influence of temperature, moisture
and pH of the medium. Under favorable conditions,
putting together these various factors, one
estimates that the population of micro-organisms can
double every 20 minutes... Therefore starting from
a few micro-organisms placed in a favorable medium, a
true contamination can occur in less than one day. The
bacterial growth curve comprises a phase of
logarithmic increase followed by a stationary phase,
then by a phase of decline when food is suddenly
lacking.
-
-
- Micro-organisms
needs
|
|
Needs
|
Bacteria
|
Molds
and yeasts
|
|
Light
|
no
|
no
|
|
Medium
pH
|
Alcaline
|
Acid
|
|
Temperature
|
20
to 40 °C
|
20
to 35 °C
|
|
Nutrients
|
Nitrogen,
Hydrogen, Carbon
|
Nitrogen,
Hydrogen, Carbon
|
|
Presence
of oxygen
|
O2
or inorganics : SOx,
NOx
|
O2
|
-
- Which
are the signs of a microbial invasion in an aqueous
product?
-
- In
general, one observes changes, in the color of the
surface, viscosity, value of pH accompanied by odors
and gaseous emissions as well as variations in the
behavior of the product. One can determine the level
and type of contamination by using indicators
containing gelose which make it possible to grow
micro-organisms quickly (48 to 96 hours), to quantify
and identify according to appearance, bacteria, yeasts
or mushrooms.
-
-
- Hygiene
of manufacturing :
-
- The
hygiene of manufacturing often takes place at the
beginning of a bacterial contamination, on this matter
it is necessary to take care of the following points:
-
- Treated
water
- To
introduce a biocide at the beginning of manufacturing
- To
protect liquid organic additives by a biocide
- To
entirely clean up facilities
- To
use disinfectants during cleaning
- To
avoid complex and difficult to clean piping(dead
lines)
- To
keep pipes and containers empty and dry when not in
use
- Beware
of dust.
-
- In
ceramics :
-
- 1)
In liquids :
-
- The
majority of disorders seen in liquid glazes are due to
bacterial activity which strongly modifies viscosity
and produces odors.
-
- These
disorders generally occur with natural products
containing organic matters (e.g. clays), under the
effect of heat and minerals concentration (High
density of liquid glazes). For sure, if the glaze
contains glue, it is even worse because the organic
matters of the adhesives are very appreciated
nutrients by bacteria.
-
- There
are often two distinct phases in the deterioration of
viscosity in the event of bacterial attack :
- -
Fluidification due to the consumption of the
components of the adhesive(glue) used in the glaze.
- -
Flocculation or thickening due to the acid dejections
of bacteria following the consumption of the organic
elements of glazes. It is then necessary to rectify
this situation by correcting the parameters of
viscosity by adding adhesive or deflocculant in the
glaze containers.
-
-
- 2)
In porous moulds :
-
- The
storage and maintenance of porous resin moulds for
casting under high pressure require an anti-bacterial
and anti-fungic action. The mould capillary network is
rather large (10 to 20 µ) and clay fines
penetrate into it. Bacterial activity, in the mould
layer impregnated with fines, leads to the filling of
the pores not easily curable by chemical action(When
this filling is on the surface, the mechanical action
of a high-pressure water spray makes it possible to
cure this problem). The best solution consists in
permanently having an anti-bacterial and anti-fungic
preventive action during the startup of the mould, for
its cleaning and its storage.
-
-
- The
role of biocides :
-
- Biocides
are products with anti-bacterial and anti-fungic
action. They are products for preventive action,
generally used at very low doses (high cost, toxicity)
and their action on the rheology of liquid glazes is
not to be neglected (due to the biocide pH ).
-
- The
most current biocides are introduced at the beginning
of the preparation, in the mixing water at a rate of
0,05% to 0,50% by weight.
-
- In
ceramics, biocides which are bactericide-fungicide
with broad spectrum activity, containing sulphureous
aliphatic and heterocyclic compounds of low toxicity,
are often used.
-
- Careful,
in too low doses, these products will not have the
expected effect and will give a false sense of
security because they can under certain conditions
favour a selective adaptation on the part of the
micro-organisms. In too large doses, they will be too
expensive, their toxic effects will be enhanced, and
risks of pollution are possible.
-
-
- Some
french companies specialized in the use of biocides in
ceramics :
-
- THOR
S.A.R.L
- 325,
rue des Balmes
- Z.I.P.
- 38150
Salaise-sur-Sanne - FRANCE
- tel
: 04.74.11.20.00
- fax
: 04.74.29.65.35
|
- SEPPIC
- Givaudan
Lavirotte
- 56,
rue Paul Cazeneuve
- 69008
Lyon - FRANCE
- tel
: 04.78.61.55.42
- fax
: 04.78.61.55.94
|
- ZSCHIMMER
& SCHWARZ - FRANCE
- 10,
rue Saint-Marc
- 75002
Paris - FRANCE
- tel
: 01.42.33.10.33
- fax
: 01.40.26.23.81
|
- LAMBERT-RIVIERE
S.A.
- 17,
avenue Louison Bobet
- Val
de Fontenay
- 94132
Fontenay-sous-bois - FRANCE
- tel
: 01.49.74.80.80
- fax
: 01.49.74.81.11
|
|