Rizal Province directory, Volume I.

SALT MANUFACTURE *
The use of solar heat for evaporating sea water and crystalizing
salt from the concentrated brine has been exploited and developed by the
coast dwellers of Manila Bay. Wide areas of Parafiaque, the leading
salt producing town of Rizal, and Malabon are appropriated for this
industry. The production begins from December to May. There are two
methods used: the Filipino and the Chinese, and both have undergone
modifications.
The native method, better known as Iras Tagalog, was probably the
first to be employed in these towns. The plant consists essentially of
evaporating ponds, leaching vats, crystalizing ponds and warehouses.
Wide areas of sandy land along the coast, and reached by the high tide
are cleared and cleaned. The soil on the surface is loosened (abuhan)
and water from canals (angkaw) through which sea water is led in,
is sprinkled over the surface where it evaporates. This process is repeated four or five times a day for three days until a heavy accumulation
of salt on the surface is obtained. On the fourth day the salt-impregnated earth is scraped into heaps and transferred to the leaching vats
where it is leached with sea water conveyed through bamboo pipes from
the estero until most of the salt is extracted. To test the concentration
of the brine, twigs of a plant called "culase" whose specific gravity is
approximately equivalent to 11.5% salt are plucked, thrown to the brine
and should they float the brine is sufficiently concentrated to be transferred to the crystalizing ponds (banigan), otherwise it is weak and
needs strengthening by dipping back into a leach several times until it
attains the required concentration.
The leaching vat is a circular dike about one half meter high and four
meters in diameter and built on the ground. The bottom is covered with
a layer of rice husks and nipa leaves which filter the mud from the brine.
The filtered brine is drawn off by means of bamboo pipes through the
dike into a shallow cement or earthernware well.
While the leaching is in progress another layer of loose soil is being
impregnated in the evaporating ponds. The leached mud after slight
hardening is marked into square blocks and as soon as the next salt-impregnated earth is scraped into heaps, these blocks are thrown back to
the field to be used again.
The floor of the crystalizing ponds are laid with smooth broken pottery set in lime mortar or cement to prevent seepage and admixture of
sand with salt. The ponds are surrounded and protected from dust and
heavy wind with bamboo fences and nipa or cogon grass. Stronger brine
is added from time to time, first passing through filter baskets to free
it from rice husks. Everyday at sundown, the salt crystals are raked
into heaps, collected into baskets to drain and finally deposited in the
warehouses.
The Chinese method consists of shallow evaporating reservoirs of
different sizes and crystalizing ponds. The lower areas usually flooded
* Excerpts taken from The Phil. Journal of Science.
104