There are two primary aspects to paint sample collection – the
packaging of the samples and the collection procedure itself.
Samples are typically collected in one of two types of packages.
Manila coin envelopes are highly recommended. They have large flaps
which should remain unsealed. There is virtually no possibility of
the sample migrating from such an envelope. The other possibility
is plastic resealable (Ziploc) bags which can be opened and reclosed
at will. The only drawback to this type of package is that labeling
can be difficult. Under no circumstances should paper letter envelopes,
sealed or unsealed, be used. If they are sent in a sealed state they
have no further value once they are opened. If they are sent in an
unsealed state the sample readily migrates from the envelope as the
flap is inadequate to contain the contents.
The samples should be labeled during the collection process. Typical
information includes the sample number, building name, building location,
name of collector, date of collection, and specific data regarding
the actual location of the sample. This can be written on the face
of the manila envelope or, in the case of the plastic bag, can be
written on it using appropriate pens or written on paper and included
inside the bag.
Collection procedures vary primarily depending on the type of substrate
encountered. In order of typical frequency substrates include wood,
plaster materials, wall coverings, hard masonry materials, and metals.
The samples are collected using a sharp metal blade such as a scalpel
or XActo knife. If the latter is used, a curved blade similar to
that of a scalpel works best.
Sample size is relatively insignificant compared to quality. Although
actual parts of a building are submitted for analysis, the sample
need not be large at all as it is viewed through a microscope. In
this case, size does not matter. What is needed is a sample with
all of its paint layers well adhered to each other and to their respective
There are cases in which the paint simply refuses to adhere to the
substrate. Typically this happens with wood elements which were originally
primed with varnish. In these cases the samples should be collected
without the substrate and if varnish was used, it will appear under
the microscope, confirming the original prime coat.
Most wood elements are milled trimwork. For these one should find
areas with an apparent heavy paint buildup. Do not look for weathered
wood, thinking that because it appears to be original, there is historic
paint on it. The wood is weathered and has lost its historic finishes
and, invariably, proves to be worthless. Look for areas that are
relatively protected from weathering. Typically vertical surfaces
are better than horizontal surfaces. Worst surfaces are areas such
as window sills. In taking the sample gently cut with the grain and
pry the sample loose. A broken surface to the cross section of the
sample is best. If the sample is cut or sawn the paint layers become
blended together. Typically, the wood splinter does not easily stop
as the grain goes farther into the wood. If one finds this happening,
then a countercut perpendicular to the grain can be made and the
splinter snapped off at the point. For those wood surfaces without
an edge sample techniques similar to those of plaster, as described
below, can be used.
Except for plaster moldings, plaster surfaces tend to be flat. Samples
from plaster moldings can be collected using techniques similar to
those described for wood edges above. For flat areas the blade can
be used to create a shallow crater, making sure that, if possible,
all of the paint is well adhered to the plaster. Again, the goal
is to reveal a complete set of layers with rough, broken edges. For
flat wood surfaces care should be taken to work with the grain. Sometimes
a thin, small, rectangular piece is cut from the wood surface.
For hard masonry surfaces such as brick, stone, and concrete the
same principles apply, although execution can be extremely difficult,
if not impossible. In a worst case scenario, the paint can be removed
to the surface of the substrate with care being taken to take samples
with complete, intact, sets of layers.
For metal surfaces there is no reasonable means of collecting the
sample with its substrate. If the metal piece is small it can be
removed and submitted for analysis. If not, the sample should be
removed as gently as possible making every attempt to remove an intact
sample. Too frequently, however, this proves to be impossible and
a scraping technique must be employed. Although this results in fragments
and dust, even this type of sample typically can be analyze with