It seems the Google Sandbox myth will never die! The so called “Google Sandbox” is purely a mental construct that webmasters tend to imagine they have been placed in when their rankings drop.
To be fair there is something known as the “Sandbox Effect” that was so dubbed after Matt Cutts admitted there is an observable ‘effect’ of Google’s algorithm that might be perceived as the cause of what many were describing as the “Google Sandbox”.
About 7 years ago Google added Trust factors to their algorithm that gives added weight to web pages that have stood the test of time. If a page had been around for years it could be “trusted” as a permanent document. These more reliable documents will rank sightly higher than an equally relevant document.
But, this change brought about another issue, new fresher information was made harder to find, so they implemented a freshness factor (QDF – Query Deserves Freshness) to boost the newest pages towards the top of the ranks for a brief period of time.
This freshness factor seems to fool new webmasters into believing that they have somehow earned this higher ranking and they are baffled once the freshness factor wears off. The so-called “Google Sandbox” is often invoked as the likely culprit. It never seems to cross their minds that they haven’t legitimately earned those higher rankings.