2. Insert Size

     To keep the inserting machine running at its maximum efficiency, envelopes should be:
• Approximately ½" longer than the longest insert, plus the thickness of the inserts if bulky.
• Approximately ½" wider than the largest insert, plus the thickness of the inserts if bulky.
     An extra 1/8" added to these allowances assures trouble-free inserting on automatic equipment.
     IMPORTANT: Inserts should be designed to allow address information, including 11 digit Delivery Point   Barcodes, to be clearly readable throughout the insert’s full range of motion within the window area.

5. Flaps

For a smooth inserting operation, the seal flap on diagonal seam envelopes should be designed with a shoulder. (The shoulder is the distance between the flap score line and start of the flap taper). Flaps cut without a shoulder can create problems on some inserting equipment. Safeguard envelopes are designed with the correct amount of shoulder area to make inserting easy. Side seam envelopes also have a precisely calculated seal flap designed for all inserting equipment Problem areas to be aware of regarding envelope seal flaps and automatic inserting equipment:
Curled Seal Flaps – To avoid curling, envelope flaps should be ordered folded down and should be stored properly. Envelopes should not be stored for more than 120 days.
Shingled Seal Flaps – Shingling occurs when one flap overlaps another. Pre-addressed envelopes should be checked for shingling before they are fed into the inserting machine.

6. Window Envelopes

When you use envelopes with a window patch, the top edge of the patch must be firmly glued to the body of the envelope. This prevents the enclosures from catching on the patch during the insertion process. Window patches should lie flat without buckling. Windows should not be located closer than ½" from the edge of the envelope for optimum results.

Normal size open face window envelopes (no patch) can be run on most inserting equipment. It is recommended that the window be at least ½" from any edge and ½" from the throat of the envelope to obtain the best processing speeds. To assure efficient inserting, it is advisable to test open face window envelopes before making a final decision to use them.

7. Gumming

Mechanical sealing requires seal flap gum that is uniform and adheres quickly and firmly when moistened. To prevent the inserting operation from pulling the envelope apart, the seams must also be securely glued.
An inserting machine will jam if there is even the slightest tendency for the seal flap to adhere to the envelope’s back. On many styles of envelopes, the seal flap gum is the first adhesive applied, and it is dried before the envelope goes through the folding and seam gumming process. During the manufacturing of die cut envelopes, for instance, the envelope dies do not go through another drying process, which means that the seam gum is damp when the envelopes are packed into boxes. The compression of the envelopes in the boxes may cause the damp seam gum to remoisten the seal flap gum, which in turn, may cause the seal flap to tack. This chain of events can cause problems during the insertion process.
With Safeguard envelopes, adhesive on the envelope is dried prior to packing. The seal flap and seam gum are both applied prior to the drying process, which allows all of the adhesive to dry before the envelopes are packed into boxes. This added measure assures that the envelopes will not stick together and cause problems on inserting equipment.

8. Storage

Envelopes must be properly stored to preserve their optimum running condition. They should be kept in sealed cartons until ready for use, and the carton should be stacked so that all envelopes stand on edge. The storage area should be dry and well ventilated. The length of storage time has a direct impact on the ability of the envelopes to run smoothly through automatic insertion and addressing equipment. The FIFO system – First In, First Out – should be used to achieve optimum performance.

Envelopes should not be stored for extended periods of time. The envelope paper will absorb moisture even in sealed cartons, so the longer the envelopes are in storage, the greater the chance that curling will occur.