Video - LSD Test Demo
The Hofmann test more precisely identifies LSD-25 and the Marquis reagent is helpful to rule out the dangerous NBOMe and positively identify 1P-LSD.
The Ehrlich reagent is a comparatively quick reacting reagent which changes colour within a couple of minutes. The Hofmann reagent is much slower in comparison and can take about 30 minutes to show a reaction.
Therefore, if you don't see a reaction within the first few minutes, it's best to wait for the reaction to take place. If after couple of hours there's no reaction, it's important to then test the sample with the Marquis reagent to rule out NBOMe and accurately identify the LSD sample.
A demonstration of how the Ehrlich reagent is used on a sample of a LSD blotter paper. Observe how the reaction is not instant, it takes about a minute for the colour to slowly change to purple. This is indicative of the sample containing LSD or any of its analogues (1P-LSD, ALD-52, etc.)
Another video of the same blotter tested with the Hofmann reagent. This test is very slow and takes several minutes before a color change to blue can be noticed for a positive result. Here's 2 minutes into the test, and at this point there's no colour reaction, which takes place at the 30-minute mark.