The Deterioration of Bubbles on Carded Star Wars Figures

                       by David C. Yao

     One of the most plaguing aspects of collecting carded

Star Wars figures is protecting the clear plastic bubbles

from becoming yellow tinted and cracked.  In addition to

causing a much lower value, these damaged bubbles ruin fine

objects of art that might otherwise be absolutely flawless.

Most collectors agree that the damage among Power of the

Force and Return of the Jedi carded figures reflect some of

the highest incidences of the above problems.  Why do

bubbles yellow?  What can be done to avoid these problems?

     The chief reason behind yellow and cracked bubbles

stems from the environment.  Environment conditions allow

two steps of damage to form.  First, at the molecular level,

ultraviolet (UV) light causes the plastic (acetate or

similar type of plastic) to lose some of its single bonds

and become conjugated.  Conjugation is the chemistry term

for the presence of multiple bonds between every other

carbon atom within a molecule.  This rearrangement of

electrons causes plastic bubbles to shift from the UV light

absorbing range to the visible light range, and thus,

produces the dreaded yellow tint.  The second damaging step

is the oxidation (addition of oxygen atoms or loss of

hydrogen atoms) of the plastic.  This alters the molecular

structure of the compound and, in this case, makes it weak

and easily cracked.  The oxidized compound may also be

further oxidized and worsens the problem.  Heat (as an

energy source) and humidity (water as a source of oxygen)

accelerate this oxidative damage.

     The loss of polymer additives to the plastic bubbles

may be the reason that some POTF and ROTJ figures become

yellow at a higher rate than earlier carded figures.  In

order to make plastics with certain characteristics (i.e.

clearness, rigidity, and ease of shaping), plasticizing

additives are added.  These additives have been known to leach

out of the plastic when exposed to certain solvents possibly

found in the glue holding the bubbles to the more recent

carded SW figures.  This scenario fits with the long held

theory among collectors that cheaper (and additive needing)

plastics are more susceptible to breaking down.

     What can be done to protect the bubbles?  Plastic

bubbles in an oxygen environment will slowly and eventually

breakdown (as do many other organic molecules surrounded by

oxygen).  The best protection would be a dark, dry, inert

gas filled environment.  However, this ideal method is far

from practical.  The clear plastic comic book bags are the

reasonable compromise that most collectors use.  The better

bags filter out UV light.  These bags also allow the pieces

to be stored in stable humidities.  Collectors might also

consider using anhydrous powders (the type found shipped

with electronic components) to soak up humidity within the

bag.  It is important to remember that these humidity

absorbers can only hold so much water before they need to be

replaced.  If pieces are displayed, collectors should

consider the possible sources of UV light (i.e. sunlight, UV

lamps, tanning machines, etc.).  With the proper

precautions, carded figure bubbles should be preserved for a

very long time.