ontal ribs are at the surface and
in staggered relation on opposite faces. Both the outside frames and
the vertical ribs are reinforced near the lug, where the greatest
amount of current must be carried.

The rectangular arrangement of ribs, as shown in Fig. 4, is most
generally used, although, there are other arrangements such as the
Philadelphia "Diamond" grid in which the ribs form acute angles,
giving diamond shaped openings, as shown in Fig. 6.

Pastes. There are many formulas for the pastes, which are later
converted into active material, and each is considered a trade secret
by the manufacturer using it. The basis of all, however, is oxide of
lead, either Red Lead (Pb30 4), Litharge (PbO), or a mixture of the
two, made into a paste with a liquid, such as dilute sulphuric acid.
The object of mixing the oxides with the liquid is to form a paste of
the proper consistency for application to the grids, and at the same
time introduce the proper amount of binding, or setting agent which
will give porosity, and which will bind together the active material,
especially in the positive plate. Red lead usually predominates in the
positive paste, and litharge in the negative, as this combination
requires the least energy in forming the oxides to active material.

[Fig. 5 Plate Straps and Posts]

The oxides of lead used in preparing the pastes which are applied to
the grids are powders, and in their dry condition could not be applied
to the grids, as they would fall out. Mixing them with a liquid to
make a paste gives them greater coherence and enables them to be
applied to the grids. Sulphuric acid puts the oxides in the desired
pasty condition, but has the disadvantage of causing a chemical action
to take place which changes a considerable portion of the oxides to
lead sulphate, the presence of which makes the paste stiff and
impossible to apply to the grids. When acid is used, it is therefore
necessary to work fast after the oxides are mixed with sulphuric acid
to form the paste.

In addition to the lead oxides, the pastes may contain some binding
material such as ammonium or magnesium sulphate, which tends to bind
the particles of the active material together. The paste used for the
negatives may contain lamp black to give porosity.

Applying the Paste. After the oxides are mixed to a paste they are
applied to the grids. This is done either by hand, or by machine In
the hand pasting process, the pastes are applied