TREATMENT FOR CONDENSATION ON HISTORIC GLASS AND STORM SASH


PART 1---GENERAL

1.01 SUMMARY

     A.   This procedure includes guidance on cleaning and
          protecting glazing against condensation.

     B.   This procedure should NOT be used on wood windows with a
          shellac finish.  The alcohol mixture recommended for
          treating condensation will destroy the finish.

     C.   Safety Precautions:

          1.   DO NOT save unused portions of stain-removal
               materials.

          2.   DO NOT store any chemicals in unmarked containers.

          3.   EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
               SOLVENT IS USED.  USE RESPIRATORS WITH SOLVENT
               FILTERS.

               NOTE:  SOME OF THE SOLVENTS LISTED ARE KNOWN
               CARCINOGENS AND MAY BE BANNED IN SOME STATES.

          4.   No use of organic solvents indoors should be
               allowed without substantial air movement.  Use only
               spark-proof fans near operations involving
               flammable liquids.

          5.   Provide adequate clothing and protective gear where
               the chemicals are indicated to be dangerous.

          6.   Have available antidote and accident treatment
               chemicals where noted.

     D.   See 01100-07-S for general project guidelines to be
          reviewed along with this procedure.  These guidelines
          cover the following sections:

          1.   Safety Precautions

          2.   Historic Structures Precautions

          3.   Submittals

          4.   Quality Assurance

          5.   Delivery, Storage and Handling

          6.   Project/Site Conditions

          7.   Sequencing and Scheduling

          8.   General Protection (Surface and Surrounding)

          These guidelines should be reviewed prior to performing
          this procedure and should be followed, when applicable,
          along with recommendations from the Regional Historic
          Preservation Officer (RHPO).

1.02 DEFINITIONS

     A.   Condensation in building terms is the process by which
          water vapor, a gas, changes to a liquid.  There is always
          water vapor in the air, the amount depending upon the
          local climatic conditions.  Within a building, the amount
          of water vapor depends upon the amount of vapor generated
          by the users.  Air has the ability to hold water vapor in
          accordance with the temperature of the air.  The higher
          the air temperature the more water vapor the air can hold
          and vice versa.  When the air is saturated it has reached
          the dew point.  If the temperature drops, the air can no
          longer hold all the water, so the excess is changed back
          into liquid form. 

     B.   Surface condensation occurs on any building material
          whose temperature is lower than the dew point, but it is
          only visible on surfaces which are nonabsorbent, such as
          window glass in winter and exposed cold water pipes in
          basements in summer (surfaces which are nonabsorbent.) 


PART 2---PRODUCTS

2.01 MATERIALS

     NOTE:  Chemical products are sometimes sold under a common
     name.  This usually means that the substance is not as pure as
     the same chemical sold under its chemical name.  The grade of
     purity of common name substances, however, is usually adequate
     for stain removal work, and these products should be purchased
     when available, as they tend to be less expensive.  Common
     names are indicated below by an asterisk (*).

     A.   Xylol:

          1.   Any of three toxic, flammable, oily, isomeric,
               aromatic hydrocarbons that are di-methyl momologues
               of benzene and are obtained from wood tar, coal
               tar, or petroleum distillates;  Also a mixture of
               xylenes and ethyl-benzene used chiefly as a
               solvent.

          2.   Other chemical or common names include Xylene; P-
               xylene; 1,4-dimethyl benzene.

          3.    Potential Hazards:  TOXIC AND FLAMMABLE.

          4.   Available from chemical supply house, hardware
               store, paint store or printer's supply distributor.

          -OR-

          Toluol:

          1.   A liquid, aromatic hydrocarbon that resembles
               benzene but is less volatile, flammable and toxic;
               Is produced commercially from light oils from coke-
               oven gas and coal tar and from petroleum, and is
               used as a solvent, in organic synthesis and an
               antiknock agent for gasoline.

          2.   Other chemical or common names include Toluene.

          3.    Potential Hazards:  TOXIC AND FLAMMABLE.

          4.   Available from chemical supply house, hardware
               store, paint store or printer's supply distributor.

     B.   Glycerin (or Glycerine):

          1.   A sweet syrupy hygroscopic trihydroxy alcohol
               usually obtained by the saponification of fats and
               used especially as a solvent and plasticizer.

          2.   Other chemical or common names include Glycerol;
               Glyceryl hydroxide; Glycyl alcohol; 1,2,3-
               propanetriol; Propenyl alcohol.

          3.   Potential Hazards:  FLAMMABLE.

          4.   Available from chemical supply house, drug store or
               hardware store.

     C.   Methyl Alcohol:

          1.   Other chemical or common names include Carbinol;
               Methanol; Methyl hydrate; Methyl hydroxide;
               Methyllic alcohol; Colonial spirits*; Columnian
               spirits*; Green wood spirits*; Manhattan spirits*;
               Pyroligneous spirit*; Pyroxylic spirit*; Standard
               wood spirits*; Wood alcohol*; Wood naphtha*; Wood
               spirit*.

          2.   Potential Hazards:  TOXIC AND FLAMMABLE.

          3.   Available from automotive supply distributor,
               chemical supply house, dry cleaning supply
               distributor, drugstore or pharmaceutical supply
               distributor, hardware store, paint store, or
               photographic supply distributor (not camera shop).

     D.   Caulk

2.02 EQUIPMENT

     A.   Clean cloths for drying

     B.   Caulking gun


PART 3---EXECUTION

3.01 EXAMINATION

     A.   Before proceeding with steps to clean and protect glazing
          against condensation, first determine the cause and
          extent of the problem:

          1.   Determine the age of the structure and of the
               glazing.

          2.   Examine the condition of the window components.

          3.   Is glass free of embedded dust?

          4.   Check for cracked, broken, chipped, or otherwise
               damaged glass.

3.02 PREPARATION

     A.   Protection:  Provide adequate wash solutions (i.e. water,
          soap and towels) before starting the job.

     B.   Surface Preparation:  Remove all oil, dirt, and other
          materials from the glass and any metal framing members by
          means of proper solvents (xylol or toluol). 

3.03 ERECTION, INSTALLATION, APPLICATION

     NOTE:  APPLY TREATMENT EVERY TIME THE GLASS IS WASHED (WINTER,
     SPRING, SUMMER, FALL)

     CAUTION:  DO NOT USE THIS PROCEDURE ON WINDOWS WITH A SHELLAC
     FINISH.  THE ALCOHOL MIXTURE WILL DESTROY THE WOOD FINISH.

     A.   Apply mixture of equal parts of glycerin and methyl
          alcohol to the inside of the glass with a clean cloth. 

     B.   Clean excess solution from glass, frames and sash
          promptly.

     C.   Clean adjacent surfaces if spills have occurred.

     D.   If storm windows are in place, identify location of
          condensation (interior sash or exterior sash) and make
          necessary adjustments to reduce condensation.

          1.   Sweating on inside of interior sash is the result
               of cold air infiltration around the exterior sash. 
               Caulk around exterior sash to eliminate
               infiltration.

          2.   Sweating on the inner face of the exterior sash
               indicates warm air infiltration around the interior
               sash.  Caulk around interior sash to eliminate
               infiltration.

                              END OF SECTION