.isotope,
.isotope .isotope-item {
  /* change duration value to whatever you like */
  -webkit-transition-duration: 0.8s;
     -moz-transition-duration: 0.8s;
       -o-transition-duration: 0.8s;
          transition-duration: 0.8s;
}

.isotope {
  -webkit-transition-property: height, width;
     -moz-transition-property: height, width;
       -o-transition-property: height, width;
          transition-property: height, width;
}

.isotope .isotope-item {
  -webkit-transition-property: -webkit-transform, opacity;
     -moz-transition-property:    -moz-transform, opacity;
       -o-transition-property:         top, left, opacity;
          transition-property:         transform, opacity;
}