Dated 2004, Portal I is one of the few works in the collection with a confirmed date, and it is one of the most formally resolved watercolors Sidney made. The composition is organized around a luminous white center — not a blank center but an active one, a space of concentrated light from which the surrounding elements seem to radiate outward. Against this center, five primary forms are arranged: three large geode-like ovals (two in the upper left quadrant, one at center, one at lower left) and at upper right a more chaotic organic mass in orange-yellow-pink that functions as a counterweight to the geometric regularity of the geodes.
The geode forms are extraordinary. Each is painted with concentric rings of color that follow their irregular edges — pink through red through orange through coral — with dark outlines that give them the quality of cross-sections, of sliced specimens. The largest, at upper left, carries an eye-like element at its interior — a small circle within the ring structure that stares outward with uncanny effect. The dotted lines that connect the forms — chains of small marks traversing the center space — function like the notation lines in a musical score, connecting elements that are otherwise separate.
The border of the composition is a dense field of small marks in blue-black — irregular, painterly, functioning as a frame that has grown from the painting itself. This self-generated border appears in several of the large watercolors and is one of Sidney's most distinctive compositional signatures.
The title Portal names the white center: it is an opening, a threshold, a place through which something might pass. The geodes are arranged around it as if in attendance or worship. This is a sacred geometry in watercolor.