<P> Supercritical CO represents an alternative to PCE, however it is inferior in removing some forms of grime . Additive surfactants improve the efficacy of CO Carbon dioxide is almost entirely nontoxic . The greenhouse gas potential is also lower than that of many organic solvents . </P> <P> Consumer Reports rated supercritical CO superior to conventional methods, but the Drycleaning and Laundry Institute commented on its "fairly low cleaning ability" in a 2007 report . Supercritical CO is, overall, a mild solvent which lowers its ability to aggressively attack stains . </P> <P> One deficiency with supercritical CO is that the conductivity of this solvent is poor . As mentioned in the Mechanisms section, dry cleaning utilizes both chemical and mechanical properties to effectively remove stains . Friction occurs when the solvent interacts with the surface of the fabric and this dislocates some dirt . At the same time, the friction also builds up an electrical charge . Fabrics are very poor conductors and so usually, this build - up is discharged through the solvent . This discharge does not occur in liquid carbon dioxide and the build - up of an electrical charge on the surface of the fabric attracts the dirt back on to the surface, which results in a poor efficiency in the washing process overall . To compensate for the poor solubility and conductivity of supercritical carbon dioxide, research has focused on additives . For increased solubility, 2 - propanol has shown increased cleaning effects for liquid carbon dioxide as it increases the ability of the solvent to dissolve polar compounds . </P> <P> Machinery for use of supercritical CO is expensive--up to $90,000 more than a PCE machine, making affordability difficult for small businesses . Some cleaners with these machines keep traditional machines on - site for the heavier soiled textiles, but others find plant enzymes to be equally effective and more environmentally sustainable . </P>

Describe dry cleaning in the context of dissolving process