Grass makes only the type 802 Pen Stylus, which is a 5" long pen with an aluminum pen shell and stainless steel tubing. There is a version #802PT that includes the plastic tubing and plunger for older obsolete Ink Reservoir systems. The 802 Pen Stylus fits ALL Grass recorders. Early pens had a stainless steel tubing with the tip "fluted" to provide a small tip to obtain a fine line. These early pens could be sharpened to provide a very fine line, but would dull with the abrasiveness of the chart paper. The #802 pen has a sapphire tip and is "honed" so the tip rests flush on the chart paper preventing "puddling" when the chart paper is stopped. Occasionally a sapphire will crack and puddling occurs - the pen must be replaced.

The #801 Pen Mount is the "cradle" that mounts at the top of the oscillograph shaft and adapts the pen to the shaft. A torsion spring provides the exact pressure of 5 grams - there is no adjustment. An Allen screw secures the adaptor to the shaft and pen spacing is achieved by loosening the screw, positioning the pen and tightening the screw. On older Grass recorders, the adaptor was insulated from the oscillograph shaft with a fiberglass bushing. This allowed polarity reversal by simply reversing the connector at the oscillograph. On newer systems using the Model 711G and 811G oscillographs, there is no bushing. Pen polarity is switchable with a switch on the 7DA Driver amplifier, 7P511, and 7P122 amplifiers.

Grass inks are water based and the formula includes alcohol, glycerine, and an anti-bactericide to prevent fungus growth. This formula provides the writing qualities desired for this type of recording. Additionally, characteristics such as pH, etc. are compatible with the Grass chart paper. Since the ink is water based, evaporation over time causes the ink to become more viscous causing skipping and longer drying times which causes annoying smudging of the records. The ink essentially becomes like syrup. The only solution is to flush the entire system, inkwells and pens, preferably with Grass IF-100 ink flush, and to replenish the system with fresh ink. Busy EEG and Sleep labs tend to use up the ink before this problem occurs; not so busy labs run into this problem. Note the availability of the Model UG-1 Users Guide at no charge which explains the use and maintenance of Grass Writer Units.

Refer to the Grass Technologies Online Store and click on Maintenance for the listing of these products and current pricing.