Bullseye COE90

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Bullseye COE90 is an art glass with a COE (coefficient of thermal expansion) of 90, manufactured by Bullseye Glass in Portland, Oregon, USA. It is the industry-standard glass most widely used for all types of kiln work—including fusing, slumping, casting, pot-melting, and pâte de verre—and is used in studios around the world. Its annealing point is Tg = 482°C and its softening point is Ts = 677°C, defining the physical property standards for the COE90 series.

Bullseye makes a vast amount of technical documentation (the TechNote, TipSheet, and ProjectSheet series) available free of charge, providing scientifically grounded information on firing programs, annealing calculations, and material properties. The color code system (4-digit numbers: transparent series 1xxx, opaque series 0xxx) is well-organized, making color management easy. The Bullseye COE90 series is characterized by its high suitability for Pâte de Verre (sintering parameter Sc) and a relatively low risk of opacity loss. In this paper, Bullseye COE90 is used as the reference system for viscosity-temperature curves.

Physical Data

熱膨張係数（COE）90 × 10⁻⁷/°C。annealing点（annealing point）482°C、歪点（strain point）438°C、軟化点（softening point）677°C。フルfusing温度 約804°C。

Product Features

The global standard for colored glass used in kiln work. With a wide range of colors available, technical resources such as TechNotes, TipSheets, and ProjectSheets—covering firing programs and material properties—are provided free of charge, making it easy to use for both learning and creating artwork.

Country of Origin

United States (Portland, Oregon). Manufactured by Bullseye Glass Co.

Related Concepts

By comparing OYF (oyf-glass), Oceanside System 96 (oceanside-system96), Effetre Murano (effetre-murano), and the η-T-t framework (eta-t-t-framework), we can understand the differences in the physical properties of each glass system and their impact on firing design.