TM 1-1500-204-23-9 NOTE The   wrong   thinner   may   destroy   certain characteristics     of     a     coating     material without immediately giving visual evidence in the wet state. viscosity    due    to    evaporation    will    require    corrective additions.      However,   some   coatings   which   undergo chemical processes, such as polymerization to create a film,   cannot   be   thinned   beyond   a   certain   point   and remain  useable;  nor  can  they  be  brought  back  to  the correct  viscosity  by  thinning  after  the  chemical  action has progressed beyond a critical point.  This is the case with epoxy and polyurethane. (2) Thinning   shall   be   controlled   by   weight, volume,    or    viscosity    measurement    to    obtain    and maintain proper and uniform consistency.  If there is no specification   covering   the   coating,   thin   according   to manufacturer's instructions. NOTE Do     not     mix     coatings     of     the     same specification    but    supplied    by    different manufacturers   during   application.      This will  avoid  problems  of  incompatibility  in the liquid and curing phases. (3) Strain   all   material   to   be   used   in   spray equipment through clean 60-90 mesh metal strainers in accordance    with    paint    or    equipment    manufacturer's instructions. n. Painting  Difficulties  and  Remedies.      Common painting  difficulties  and  ways  to  fix  them  are  described in the following paragraphs. (1) Coating  troubles.    Coating  troubles  may be   divided   into   six   groups:      (1)   Inadequate   surface preparation (including temperature), (2) incorrect methods  or  techniques  of  application,  (3)  unusual  and unsuitable    climatic    and    atmospheric    conditions,    (4) unsuitable and improperly adjusted equipment, (5) faulty finishing    surface    or    improperly    mixed    or    agitated components  and  (6)  systems  not  purged  of  previously mixed   materials.      An   experienced   finisher   may   be capable  of  adjusting  to  obtain  proper  results  with  faulty materials,  but  this  is  an  emergency  measure  only  and must be with the cognizance and authority of the quality control  facility.    The  practice  is  not  advised.    Incorrect methods   of   application   should   be   discontinued   upon discovery of the discrepancy.  Areas painted prior to the discovery of such discrepancies must be inspected and remedial measures  taken  when  necessary.    Brushing  and  roller coating  on  certain  surfaces  must  be  used  in  confined areas.  Remedying incorrect applications, however, also calls for training.  The practice of allowing inadequately trained  personnel  to  apply  Military  Specification  MIL-C- 46168 coatings is unauthorized and dangerous. Unusual or unsuitable climatic and atmospheric conditions   are   normally   not   a   problem   since   manual spray  painting  must  be  accomplished  in  an  approved facility  which  usually  compensates  for  such  conditions. Unsuitable or faulty equipment can only be remedied by obtaining     proper     equipment     or     repair.          TM     55- 150034523   shows   common   troubles   of   spray   coating operations'   with   suggested   remedies   or   methods   of avoidance. (2) Spray patterns.  Faulty spray patterns and suggested corrections are shown in TM 55-1500-34523. (3) Blushing.      Blushing   of   coatings   is   the result    of    water    condensation    from    the    atmosphere within, or on, an applied organic film.  It occurs when the temperature    of    the    work    surface    falls    below    the prevailing  dew  point.    (It  shall  always  be  looked  for  in production     coating     whenever     other     than     average atmospheric  conditions  prevail.    )  It  shows  as  a  lighter than   normal   or   bleached   discoloration   or   increased opaqueness of the film.  It may occur to the extent that a surface   powder   develops   which   can   be   removed   by fingernail or by light rubbing.  (Rubbing will not cure the condition.      )   It   may   be   almost   imperceptible,   and blushing inducing conditions may escape notice on test panels  sprayed  prior  to  production  coating  due  to  the temperature   differences   between   test   and   production environment.    Though  MIL-C-46168  painted  items  are not susceptible to water or moisture damage immediately after proper application to items, great care must  be  taken  to  avoid  surface  condensation  prior  to coating  or  water  induction,  in  any  form,  into  unmixed components or the mixture prior to or during application. Water   will   not   affect   the   cure   process   after   proper application.    Water  will  affect  paints  other  than  plural component catalytic paints. o. Finish   Painting.        MIL-C-46168    is    the    Army standard tactical topcoat for ground support equipment. (1) Preparation  of  MIL-C-46168  polyurethane paint.      Preparation   of   this   paint   is   detailed   in   the following procedures: (a) Polyurethane,  MIL-C-46168  paint  is a plural component, low reflective paint formulated to be lead  and  chromate  free.    The  components  of  this  paint must   be   thoroughly   mixed   prior   to   pouring   into   the application container when transfer is necessary.  Care 9-13