When a slide is stuck or has been glued in, you can inject a little water and a small amount of heat to free up the slide.

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Note mixing needles also work good for injecting a little bit of hyde glue in just the right area. Hyde glue will dry inside the needle. To clean the needle, put water in the syringe and then use a heat gun to heat up the needle while you apply pressure. The water will start to squirt out, continue until it's completely clean.