1/8-inch Mesh Screen

One of the main things I have taken on concerns screen size.  Here in the Northwest, the trend has been towards using fine mesh (1/8-inch mesh) for all archaeological investigations.  This is not simply sub-sampling with fine mesh, but processing all excavated sediment through fine mesh.  

There are many reasons for this trend, with probably the biggest being the emotional appeal.  That is, it just seems more science-y.  It feels right.  It feels rigorous.  We get lots more stuff and since archaeologists want stuff, isn’t more stuff better?  

What’s always missing, however, is a discussion of what we are losing by only using fine mesh.  I often get strange looks when I ask this question.  “We are not losing anything,” is the response, “that’s why we are using fine mesh.”  Unfortunately, you are losing stuff.   Lots of it.   

I have said it before and will say it again. The dramatic increase in the use of fine mesh is a disaster for regional archaeology.  

Clearly, important information is found in fine mesh.  But more of the most important information is found in the 1/4-inch screen.  Nearly all tools are found in 1/4- inch.  The vast majority of identifiable faunal remains are found in 1/4-inch.  Using 1/4-inch allows excavation of a larger portion of a site for a particular amount of money.  Excavating more of site means more features.  Finding features is more closely related to area (or volume) excavated than screen size.  Excavating more of a site also means more information on different parts of a site.  

And for a change, let’s be honest about this.  We all know what happens when field crews are faced with trying to push clay through 1/8-mesh.  They end up throwing most of it away (after spending vast amounts of time pushing sediment around a screen, of course).  Just ask a field tech (preferably one who is not working for you and after they have had a few beers).  They will admit it.  It’s not that they are bad or evil.  It’s just that 1/8-inch mesh sucks to screen through. 

Here is another thought.  Almost all information used to evaluate precontact sites for the NRHP is found in the 1/4-inch mesh or is related to area/volume excavated.  Tools, features, temporally diagnostic artifacts, indefinable faunal materials are all more common in 1/4-inch mesh.  When you only use 1/8-inch mesh you have to dig less of a site for the same budget.  You have to; there is no way around it.  Thus, you are collecting fewer tools and temporally diagnostic artifacts and finding fewer features. 

What mystifies me is when you only use fine mesh, how you can claim to ever be evaluating precontact archaeological sites.  When you only use fine mesh you are actually selecting against those data classes most commonly used to establish eligibility.