TM 1-1500-204-23-1 (a) Open   curing   agent   Pro-Seal   890A and  thoroughly  mix  it  In  the  container  until  it  becomes  a smooth paste. (b) Thoroughly  mix  10  parts  of  Pro-Seal 890A to 100 parts of Pro-Seal 890 by weight, or 8.4 parts of Pro-Seal 890A to 100 parts of Pro-Seal 890 by volume. (c) Carefully fold the material upon itself and  blend  for  a  period  of  at  least  five  minutes  This  will give a satisfactory mix. NOTE Avoid violent agitation In order to beat as   little   air   Into   mixture   as   possible Also,   frictional   heat   developed   from violent  agitation  may  reduce  work  life of the material. (5) Curing     requirements     for     Pro-Seal     890 sealant (2 cure option).  Requirements are as follows: • Mixed,  uncured  Pro-Seal  890  sealant  material (Class  A-2  or  B-2)  requires  72  hours  at  room temperature for a full cure. • If the production schedule is not flexible enough to   allow   for   the   long-time   room   temperature cure, accelerated step curing conditions may be employed  to  fully  cure  the  sealant  material  In four  hours  at  elevated  temperatures  The  step curing    conditions    are    two    hours    at    120 °F (49°C),  followed  by  an  additional  two  hours  at 158°F (70°C).  This means that you should use two ovens set at the two different temperatures specified   to   fully   cure   the   uncured   material under accelerated conditions. d. Repair   of   Armor   Plating.      Specific   repairs   and Inspections    for    armor    plating    are    described    in    the following paragraphs. (1) Repair and inspection of cracked tile Repair and Inspection procedures are as follows: (a) Inspect for cracked tiles. NOTE Multiple cracks converging at an angle of 15 degrees or less are not repairable.    You    may    repair    cracks occurring in the ceramic tile 1/16 of an inch or less In width, provided that the backing Is not damaged beyond repair.      Do   not   repair   armor   panels where  a  crack  (or  cracks)  wider  than 1/16    if    an    Inch    is    found.        Total allowable   defects   are   three   or   less cracks,  chips,  or  spalls  in  any  2-inch square area. (b) Repair  cracked  tile  by  bonding  a  1/8  inch thick  sheet  of  fiberglass,  type  GEE,  MIL-P-18177,  over the  crack  (or  Cracks)  overlapping  the  damaged  area  by three  (3)  inches  on  each  side,  using  Polysulfide  Sealant Pro-Seal 890 (FSCM 83527). (c) Bevel  all  edges  of  the  fiberglass  patch  1/4 Inch  deep  and  30  degrees  from  the  top  surface  so  the nylon spa shield will fit smoothly over the patch. NOTE For ceramic having raised edges at the joints,  one  side  of  the  patch  may  be cut     short     of     the     3     inch     overlap requirement.        If    the    crack    extends through   a   raised   edge   on   the   tile, shape the patch, by undercutting, to fit over    the    raised    edge.        Use    good judgment in determining this, bearing. In   mind   that   the   patch   is   to   restore structural  integrity  of  the  panel  When patching along a panel edge, cut patch to fit the edge boundary along periphery of the tile. (d) Remove existing sealant residue from the   tile   surface   by   using   a   solution   consisting   of   50 percent by volume of Petroleum Distillate Base, TT-T-291 and Toluol, TT-T-548. (e) Lightly   abrade   the   fiberglass   patch and ceramic surface surrounding the cracked area where the patch (or patches) is to be bonded. (f) Clean the abraded ceramic and patch surface using a clean cloth moistened with methyl ethyl ketone, TT-M-261.  To obtain satisfactory adhesion, apply sealant only to a clean dry surface, free of oil and grease. 9-51