Previously, we successfully synthesized 400-mer oligos and employed the CBP method to isolate the full-length oligos from the complex mixture of crude products. The key elements that contributed to the success include using controlled pore glass (CPG) with a large pore size of 2,000 Å as the solid support and reducing its loading by inactivating a portion of the reactive sites. These adjustments reduced the steric hindrance of the CPG, which we believe is crucial for the efficient synthesis of long oligos. Realizing the unlimited power of the CBP method for isolating low percentages of full-length oligos in the course of that work, we reasoned that if the steric hindrance can be further reduced, even longer oligos can be synthesized and isolated. Instead of reducing the loading of CPG further, we considered conducting the synthesis on smooth surface as opposed to within pores of solid supports. A typical concern for this approach is insufficient loading, which may be the major reason for traditional oligo synthesis to be conducted in pores. With the potential loading problem in mind, we thought that glass wool would partially solve the problem. Therefore, we calculated the loading of glass wool, and made a comparison with that of glass beads (Table ).