Some things just go together: April and taxes, Bill
Clinton and Big Macs, paste and pasting machines. That, of course, is only
fitting and proper: Adhesives and pasting machines were made for each other.
But it's not always love at first sight, as we shall see.
When the first pasting machines were imported from
Europe 20 years ago, it must have been something akin to prehistoric man
staring at the first wheel -- the machines looked impressive, but what
could they do? The sole reason pasting machines were invented was to provide
an alternative to hand-pasting, which can be time-consuming and inexact.
Pasting machines, therefore, are designed to apply an even coat of adhesive
quickly and evenly.
It really doesn't take any special skills to operate
the machine. In fact, you're already halfway there. "Think of 
the pasting machine as a tool to which
you can apply all your hand skills, rather than a new skill to learn,"
said Certified Paperhanger and PWC contributor Bob Kelly. "Most hand
skills transfer to using pasting machines."
Sounds easy enough, but don't pour in the paste and
get started just yet. In any partnership, the chemistry's got to be just
right for it to succeed. The adhesive is a primary variable in each paperhanging
job, and your choice -- and consistency thereof -- should be affected by
your method of application. Paste and pasting machines, partners.
Meet your machine: Get to know the machine you'll
be using. How exactly does the paste reach the paper? In most pasting machines,
by means of a roller. The roller picks up the adhesive from a tray, then
depending on the machine, the adhesive will travel directly to the back
of the wallcovering, or to another roller before it reaches the wallcovering.
The thickness of the adhesive can be regulated (again, depending on the
machine) by moving the rollers or the roller and a scraper bar closer together
or further apart.
"Pasting machines require a product that will
break down and flow around the roller to make application easier,"
said Kay Peters, technical director for Evans Adhesive. "If you have
a product that doesn't break down with agitation, you may have problems
using it in a machine."
Generally, clears provide a consistency that performs
better in machines than the thicker clay-based adhesives, said Jeff Keelan,
director and owner of The Paperhanging Institute in Fairfield, NJ. Still,
there will be occasions when you want to use a clay-based, so "you
have to know if your machine can tolerate certain kinds of adhesives,"
Keelan said.
Peters advised first and foremost that paperhangers
read adhesive labels carefully. "Most products made for
pasting machines will say so on the label,"
she said. But even after you've identified an adhesive as "machine
grade," you might want to check its consistency. Stir it. If it fails
to thin or become "flowable," you've got three choices: pour
it in and keep your fingers crossed, pass it up for another kind, or thin
it yourself.
"I always tell people the machine will not adjust
to the adhesive, so you've got to make the adhesive adjust to the machine,"
said Robert Lorist, the original designer of the Paste-Mate pasting machine
sold by Advance Equipment. "If you use a lightweight machine (single
roller, no gear drive), you need a lighter adhesive, or an adhesive like
a clear that you can thin."
But thinning is risky, warned Kay Peters. "The
best advice would be not to add any water," she said. "But I
know people are going to, so I'd say add as little as possible. Most problems
come from adding too much water and diluting the solids of the product.
Then they have trouble getting the paste to work."
So if adding water might result in failed adhesion,
what's thin enough -- without being too thin -- for a pasting machine?
Ask a contractor and you're likely to hear "You'll know," but
Lorist offered a more scientific method: "When you use a mixer in
the bucket and you lift it up, the adhesive has to flow. You shouldn't
get one glop and have to wait one or one and a half minutes for the next
glop."
Bob Kelly recommended mixing the adhesive according
to the manufacturer's instructions and pasting a piece of wallcovering
by hand. "If it looks like it's the right viscosity, then you can
dump it into the machine. The difficulty is that once you dump it in, it's
in there. It's harder to dilute or add anything once it's in the machine."
If by choice or necessity you work with a clay-based
adhesive, you'll need a machine specifically designed to handle its thicker
consistency. In comparison to clears, clays are slower to fill the void
when picked up by pasting machine rollers, said Jeff Keelan.
"With a lightweight machine, you probably won't
use clays," he said. "If you really want versatility, use the
better machines. They can handle clay at full strength." Gravity-feed
machines, like Paste-Well's, can handle the heaviest adhesives, Keelan
added.
"I haven't really found a machine that will
pull clay easily with a single roller," said Kelly. "The ones
that tolerate clay seem to be well-engineered machines with multiple rollers.
Because clay-based adhesives don't have the same viscosity as clears, you
need more gears." In a multiple-roller machine, a bottom roller will
agitate the clay and keep it runny.
In addition, clays perform best if
a machine's paste tray is sloped or V-shaped, rather than a basic rectangular
pan, said Lorist. The slope will keep the adhesive flowing into the machine
and prevent it from settling. The paste tray is a permanent feature on
a machine and cannot be changed, of course, so you'd better know what you're
looking for going in.
Some contractors experience skips in coverage when
using clays in pasting machines. While a sloped pan should help prevent
this, you should also keep the tray filled higher with clay than you would
with clears, Keelan suggested.
De-activator: Although "thinner is better"
seems to be the rule for adhesives used in pasting machines, the machines
will not tolerate water. If you intend to use a machine with a prepasted
wallcovering, you must use an activator, which can be poured right into
the machine.
"Even though there's a large quantity of prepasted
paper going to market, the machines will not pick up water," said
Rob Henderson, market development manager for Custom Building Products.
"We introduced an activator just for that reason. The activator has
just enough viscosity to be picked up by the rollers. You should never
thin an activator. If you do, the roller will not pick it up."
Fans of pasting machines insist they're the best
thing that's happened to adhesives, reducing pasting time by as much as
70 percent. Still, there may be occasions when it's wiser to skip the machine.
"There's no way you can paste by hand as evenly
or as perfectly as you can with a machine," said Henderson. "But
if you're using a really exotic, acrylic-backed fabric, for instance, you
might want to dry-hang it to avoid any accidental staining or saturation."
Any paper that because of a special ink or coating
will mark easily, may burnish in a machine, said Kelly. "Also, there
are a lot of expensive papers that are real papers, and have to be double-pasted,"
he said. "That requires the action of the brush to work the paste
in. The action of the machine is rather mechanical, and the thickness is
more difficult to adjust than by hand."
But Keelan insists the right machine paired with
the right adhesive is a partnership not to be undone by even the most intimidating
wallcovering job. All it takes is a little practice.
"The most sophisticated machines will pull the
wallcovering through perfectly clean," he said. "I've been using
a machine for six years, I use one everyday, and I never want to see a
paste roller again."
Like steak and potatoes, like Clint Eastwood and
westerns, adhesives and pasting machines were meant for each other. All
you need to add is a little matchmaking.
Article from The Paintstore archives (www.paintstore.com).
Credit to Barbara Freidman (author), Contributions by Paul Kelly (Certified
Paperhanger and Contributor to PWC), Bob Lorst (Original Designer of PasteMate),
Rob Henderson (Custom Building Products), Kay Peters (Evans Adhesive),
Jeff Keelan (Paperhanging Institute)
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