385T Spring 2010
Treatment methods, Karen L. Pavelka, Instructor
Humidification
This subject is surprisingly complex and misunderstood. The concepts are somewhat simple and
obvious, but the variation is endless. All the methods below are variations on raising the relative
humidity, either overall or locally, in a controlled fashion. Do not think of any of the methods
described below as the “right” method; there are endless variations.
Remember that paper is 3D, not 2D and try to think about all the variations in every piece of
paper. The front is different than the back and the core is different still. Try to visualize the
paper as a mass of fibers, each expanding individually.
Overall Methods
Overall humidification can be a simple and effective treatment, but there are some cautions. The
object can become wetter than you had anticipated. The object may wet up unevenly. Some inks
can bleed in a humidity chamber. The back may become more wet than the front. Some papers
will cockle and never be flat after humidification.
Humidity Chamber This is the most common form of a humidity chamber. Select an
appropriately sized tray. Place wet blotters in the bottom, then a sheet of plastic grating, then
a sheet of nylon screen, then a sheet of polyester web. Be sure the sides of the tray are dry
and there are no stray drops of water anywhere that might come into contact with the object
to be humidified. Place the object on the web, then cover the tray with a sheet of acrylic
sheeting. The tray should be completely covered.
Ultrasonic humidification Place the object in a sealed environment and gradually raise the
humidity by inserting the hose from the ultrasonic humidifier and allowing the vapor to
circulate. It is very easy to get uneven humidification using this method. There will be drips
from the hose and you must protect the object and environment from those drips. The
enclosure can be the bubble on top of the suction table, a covered tray, a large piece of plastic
draped over the conservator and object, or anything else you might imagine.
Gore-tex Insert the object in between two sheets of Gore-tex, membrane side in, and place
wet blotters or cloth on one or both sides of the outside (felt side) of the package. Seal the
perimeter of the package with glass weights.
Spray or mist Use a Dahlia or other spray bottle to apply moisture to the object.
There are more.
385T Spring 2010
Treatment methods, Karen L. Pavelka, Instructor
Local methods
Local humidification is often necessary, but beware uneven cockling.
Damp swab Roll a lightly dampened cotton swab over the area to be humidified.
Blotters Damp blotters can be placed on an object, either with or without weight on top.
Tide lines are a danger with any method of humidification, but especially with this one.
Brushes Apply moisture with a damp or wet brush.
Ultrasonic Use the hose to direct a stream of humidity where needed.
Breath Sometimes breathing on an area of an object can provide all the moisture you need.
Obviously, no chocolate, coffee, etc., and don’t sneeze.
There are more.
Flattening
Humidified paper has expanded and if you want it to dry flat, you must restrain it somehow.
There are times when you need to retain type impression or an embossed mark and still get the
overall sheet flat. A common error is to underestimate the amount of water that can be held by a
sheet of paper; it is more than you realize.
Most paper needs to dry for at least 24 hours; sometimes much longer.
Air drying Let the liquid drain from the paper and place it on a blotter or screen. This will
result in a very cockled piece of paper. Flattening it will require re-humidification. You may
choose to air dry the paper partially, then apply some restraint.
Felts You can place an object between two or more felts to restrain it as it dries. Be sure you
protect the object from direct contact with the felt, most commonly by placing polyester web
between the object and felts. You may elect to cover the felt with a glass or Plexiglass weight
but to avoid leaving impressions in the felts, be sure the entire expanse of the felt is covered.
Be sure you have at least 6” of margin around the object, otherwise the object may be slightly
ruffled around the edges.
Blotters and boards Place an object between blotters and boards and keep changing the
blotters until the object is dry. A good rule of thumb is once the object feels completely dry
change the blotters at least two more times.
Directional drying Stains will travel through paper with water as it dries; this is the reason
tide lines form, but you can also use it to your advantage. If you want to draw the stains to
the back of a piece one technique is to air dry it to the point before it begins to cockle. Then
place the object on a piece of polyester web supported by a screen from the drying rack.
Cover the front with polyester web and then a sheet of acrylic. The idea is to force the paper
to dry to the back, thus pulling the stains in that direction.