Cranky coverslipping tape? 5 tips to ensure trouble-free coverslipping.

Common problems with coverslipping tape like air pockets under the film, bubbles, waviness, or improper adhesion can often be resolved with a few simple tips and tricks. 

1. Increase the xylene drip by 2-3 drops and ensure it's filled properly.
Xylene activates the adhesion of the tape during the coverslipping process, creating a secure and transparent seal. Some tapes benefit from more xylene than others, and increasing the xylene drip by a few drops can help resolve air pockets and bubbles around the edges of the coverslipping tape, waviness on the surface, or inadequate adhesion—especially if you've just changed brands. In addition, keep the xylene bottle filled above the probe. If the xylene bottle level is too low, it could introduce air bubbles instead of xylene. 

2. Allow tape to acclimate to your lab environment before use. 
Coverslipping tape is moisture and temperature-sensitive, and it's important to let the new product fully acclimate for at least 24 hours in the operating environment before use. 

3. Clean off adhesive build-up in the walls of the conveyor and on the rollers.
Build-up can cause lifting of the tape as it passes through the machine, preventing proper adhesion. Clean the conveyor belt and sides of the conveyor with a xylene-dipped cotton applicator and clean rollers with an alcohol-dipped cotton swab.

4. Change your blade.
If the tape is ragged around the edges or creating bubbling, try changing the blade to ensure a sharp cut and prevent unwanted artifacts.

5. Ensure sections are cut evenly and processed completely
Thick and thin sections on the same slide can cause problems when coverslipping, including air pockets, waviness, lifting of the tape around the edges or improper adhesion. If any alcohol or water is left in the tissue, the tape adhesive will not be completely activated—remember, water and alcohol don't mix! This might also be occurring if there is excess alcohol in the final xylene rinse used during staining—change the xylene in the final rinse at least once per day to ensure purity.

Still having problems? Here's a few equipment-related problems to check. 

Jamming in the machine

•  Inspect your slide basket for any bends or missing teeth. 
• Missing teeth or bends in basket will impact slide feeding onto conveyer belt and/or dispensing of coverslipped slide from conveyer belt into collection basket, causing a jam. 
• Only place 1 rack (basket) on the loader at a time.  
• Check for gummy residue on the small roller attached to sensor arm and routinely clean with xylene-dipped cotton applicator.
• If build up is too much to remove and problem persists, call service technician to clean roller. 

When changing coverslipping tape rolls:

• Manually remove any excess tape to prevent double coverslipping, coverslips extending from the bottom of the slide, and eliminate back-up or jamming of slides in the receiving rack.

Slides sticking together after coverslipping

• Freshly coverslipped slide should not be placed against another slide for 8 to 24 hours. If at any time, a user places freshly coverslipped slides together, the slides may stick together. Placing freshly coverslipped slides under a fan, in a slide rack, or on slide board to allow time to thoroughly dry before stacking or filing. 
• Ensure that slide labels are placed over the frosted area of the slide only to help eliminate excess label adhesive be transferred to conveyor belt or roller. 

Coverslipping film is not dispensing properly or film does not advance properly

• Turn the instrument off and rewind the film onto the roll. Be sure to cut off any crimped edges or ragged end pieces. Rethread as usual.

Film cutter not cutting film properly

• Cutter blade is dull and needs replacement. Blade assembly is loose and needs tightening. Blade cut limit is 10,000 cuts.

Film length is longer or shorter than it should be 

• Wrong film length has been selected. The film length defaults to ‘Long’ each time that the instrument is turned on. If using ‘Short’ alternative, you must press the ‘Short’ button on keypad after turning the unit on.

Film is not being positioned in the correct position on the slide

• The length of the slide has changed from the original setting used during the previous set up. 
• Film is not advancing properly due to being heat-stressed, or defective. Unwind the film and examine the film as it unwinds to determine if it is sticking together. 

Film is pulled up as the slide passes under the pressure roller. 

• The lower film advance roller is tacky because of a buildup of resin dust, debris, and xylene. Be sure to clean the roller and surrounding areas routinely.

Coverslipped slide has hazy or cloudy appearance 

• Xylene substitute is being used or possible xylene contamination with water.  
• Use a reagent grade xylene in the final rinse and replace it at least once each day to maintain purity.

Tape unwinds or becomes loose after installation into the machine 

• Check tension on tape after installation into coverslipper and around roller pins.

Tape has a ‘splotchy’ appearance, and the adhesive has a rough appearance. While unwinding the tape, an audible ‘sticking’ sound can be heard (much like unwinding masking tape). 

• Tape has become heat-stressed and should not be used.

Slide is skipped/ not coverslipped

• There was an error in the sensor detecting it. There may be an option on the coverslipper to adjust sensitivity.