Making a pitch lap with Acculap synthetic pitch.

Acculap is a new form of synthetic pitch.  It comes in 10 grades of hardness.  I ordered the "intermediate" grade, which is a little harder than their "standard" grade.  It is available from www.salemdist.com     It comes in an aluminum foil container that can be also used to heat up the material in.  I broke off only a small chunk to melt for this small lap.

A few minutes after pouring the pitch, I peeled the masking tape from around the edge, then I quickly pushed in grooves with the dull edge of a hack saw blade.  The pitch is still warm and alittle soft while doing this.  For larger laps, I would use the LM3 rubber pitch lap mold.

Working quickly while the pitch is still warm, I pressed in the mirror blank with alittle cerium oxide polishing slurry.

I then trimmed the lap with a knife so that the lap has a slightly smaller diameter than the mirror.  Also, the sharp edge of the hack saw blade was used to cut the channels better.

The finished lap, ready to go.  Prior to each polishing session, the lap is trimmed a bit and is warmed under a heat lamp for a few minutes until my fingernail can push into the edge of the lap.  Then the mirror is then pressed in with some polishing slurry and allowed to cool.

More comments: When cool at room temperature, the material chips similiar to regular pitch.  If you heat the lap just alittle above room temperature, it trims and cuts very nice. Since it is clear, if you do polishing with the lap on top, you can easily see the liquid and bubbles to get an idea as to when to add more liquid. This stuff only has minimal smell,  unlike regular pitch. It doesn't dry out with age.  You can set your lap on the shelf for months and then use it again without worrying about hardness.

8 inch lap                                              5 inch lap                                       3 inch lap The 8 inch lap was made on a glass blank with a few large chips on the back side.

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