# ASTM D4285

Source: https://coatmentor.com/standards/astm-d4285/ · Updated 2026-10-14

Checking compressed air for oil and water: the blotter test.

**Publisher**: ASTM International

**Area**: Surface preparation and conditions

A clean white blotter or collector is held in the air stream, after the oil and water separators, for at least one minute. Any stain of oil or water means the air would contaminate the steel it is meant to clean.

## Where it applies

The test covers every use of compressed air on the work: abrasive blasting, blowing down the cleaned surface, and spray application. Hold the collector after the separators, coolers or driers, so that it samples the air that reaches the steel.

The SSPC/NACE blast cleaning standards require clean, dry air and abrasive free of oil and grease. SSPC-SP 10 names ASTM D4285 as the check of the air.

## When the blotter shows a stain

Blasting and blow-down wait until the air supply is fixed: drain or service the separators, then test again. Steel already blasted with that air may carry oil, so check it before coating. Record the test, its time and the result in the daily report.

**4** practice items in the members area mention ASTM D4285 (CIP 1: 2 · CIP 2: 1 · FROSIO written: 1).

## Related

- **Concepts:** [Surface cleanliness grades](https://coatmentor.com/learn/surface-cleanliness/)
- **Standards:** [SSPC-SP, NACE No. and WJ](https://coatmentor.com/standards/sspc-surface-preparation/)
- **Defects:** [Cratering (fish eyes)](https://coatmentor.com/defects/cratering/)

## About this page

This page describes the subject of ASTM D4285 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the [corrections log](https://coatmentor.com/method/). CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.