4 min read
What Lightfastness Ratings Actually Mean
That little ASTM rating on your paint tube is telling you something specific — here's how to read it.
Lightfastness measures how resistant a pigment is to fading under prolonged light exposure. The ASTM scale runs from I (excellent — essentially permanent) through V (poor — will visibly fade), and most reputable artist-grade brands print this rating directly on the tube or pan.
This matters most for work that will hang in direct or indirect sunlight long-term — a painting in a sunlit room with ASTM III or IV pigments can visibly shift in color over a few years, while ASTM I and II pigments hold their color for decades.
Student-grade paints sometimes substitute cheaper, less lightfast pigments to hit a lower price point, which is one of the real (not just marketing) differences between student and artist-grade lines.
If you're selling or gifting finished work, it's worth checking the lightfastness of any color you used heavily — it's a five-second label check that prevents a disappointing conversation in five years.
