French Press Grind

The picture links were removed because Photobucket decided to change the terms of usage in mid stream, so to say,  It is inconvenient for viewers but it is better to rid yourself of such people as soon as possible.  It is the attitude as much as the action.   We will try to repair that mess at NXTroasters.com

The French Press is a classical brewer that has garnered many comments.  Often it is used for comparisons when authors are promoting a new device.   Many instructions and guides have been published yet there are recurring themes i.e. the medium grind with less than boiling temperature water.

Of course these demonstrations use freshly roasted coffee, otherwise what is the point of drinking coffee.

To the left the coffee beans were ground with a blade type grinder which is unable to attain the finer grinds.  The larger particles initially contain a lot of CO2 hence the large amount of foam.  I hesitate to call this crema because it is a mixture of foam and coffee grounds.

The foam develops very quickly when the nearly boiling water (that point will be argued later) is poured into the container.  Much of that is likely due to the sudden rise in temperature which causes the CO2 and other gases to rapidly expand, in the bean, when immersed in the hot water.

In the first minutes much of the coffee grounds are buoyed by the foam therefore they do not absorb sufficient liquid to decant.

Relying on the Mesh Plunger to do the solids / liquid separation will not give satisfactory results. Either the screen will plug with grounds and/or the screen  will deflect inwards let the ground migrate to the top of the mesh.

The argument that the grind has to be sufficiently coarse that the Mesh Plunger is not plugged ignores the importance of the extraction.  I maintain that the purpose of the Mesh Plunger is to keep the decanted coffee grounds on the bottom of the container when the coffee is poured into the cups.  The aim is to drink coffee not to have coffee grounds for breakfast.

The picture to the right was taken 1.5 minutes later.  We can see that the liquid line has risen but that more water will have to be added if the vessel needs to be full.  Very likely it will have to be filled twice to prevent the foam from overflowing.

In this case the Mesh Plunger was depressed 4 minutes after pouring the water.

                   
To the left is a coffee  ground with a  burr grinder using  a very fine setting which usually makes a variation of in the cup Turkish coffee.  The Mesh Plunger  only comes into play once the grounds have decanted.  The settling process is greatly accelerated by the fine grind which  yields grounds that have a high ratio of surface area to volume, hence a rapid and thorough extraction.

The crema, discerned from foam by the size of the gas bubbles, is similar to an espresso shot.  The brewing was well behaved therefore no water had to be added.  The brew decanted within seconds and was served sooner than the coarser grind.

The water was brought to a boil then poured over the coffee.  The comments about near boiling water scalding the beans must originate with manufacturers and distributors of machines that are unable to heat water over 85°C.  

The roasting chemical process is halted when the beans are cooled below approximately 150°C which hardly supports the claims that 90°C water scalds the beans.  On the contrary experiments show that the extraction is better developed at higher temperatures. 

Do your own experiments and note the observations.  If possible measure the temperature of the water for different extractions so that you can optimize your procedure.  In the meantime enjoy the fruits of your experiments.