We present here some new information on Guinier-Preston (GP) zones Al-5at.%Ag and Al-17at.%Ag alloys quenched from the liquid state by the two-piston technique. Such a quench is able to slow down the clustering rate by detecting the extremely early stages in the decomposition process. The scattered intensities are recorded in situ when heating the samples by means of a position-sensitive counter. The main conclusion of this study is that the liquid quench cannot entirely freeze the disordered state at high temperatures. Nevertheless, it allows us to obtain at room temperature a metastable state corresponding to GP zones which normally occurs at 190°C or at a higher temperature.