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How to Choose an Air Pen (Air Scribe) for Fossil Preparation

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Air pens or air scribes are the number one tool in fossil preparation. Essentially, an air scribe is a compressed air driven stylus or needle that repeatedly hits the rock many thousands of times per minute, removing matrix from your fossil. Air pens are the most ubiquitous type of fossil prep tool there is, found in garden sheds up and down the country all the way through to museum and professional prep labs. For a beginner, the natural progression up from an electric engraver or hand tools is an air pen before diversifying into multiple air pens and air abrasives


There are a few things to consider when purchasing an air pen. What sort of fossils are you collecting? How fragile are they? Is there a lot of hard rock that you need to remove before working on the fossil? What’s your budget? Do you already have an air pen?


Different tools do different jobs, and have different internal mechanisms which make them exceptionally good at some jobs, but relatively poor at others. All of our own-brand tools at ZOIC PalaeoTech are custom designed to fulfil a need in fossil preparation, but we do our best to make them as versatile as possible to maximise their usefulness. Whilst there are ‘general purpose’ tools to suit somebody just getting started, many professionals or advanced vocational fossil preparators have a myriad of tools; each with its own very specific niche in their work.


Whether part of our budget range, or our PRO Range, at ZOIC PalaeoTech it is important to us that we are providing you with the best 'bang for your buck' within its category compared with other providers. We have an incredible demand for our air pens, with many laboratories and preparators upgrading their set-up to a ZOIC PalaeoTech one. In the last few years, we have grown beyond what we could possibly have imagined through word-of-mouth recommendation. Our fossil preparation air pens are precision engineered to exacting standards, built with consistency for dependability and of course, enjoyability. Our innovations and designs are changing the way we approach fossil preparation, and we're always working on something new so keep checking back!


ZOIC PalaeoTech have a PRO Range (including the T-Rex, the ZOIC Chicago, Velociraptor and Microraptor) as well as our budget offering, The Trilobite. It's important to match the air tool you have for the job in hand.


fossil preparation tools

A good tool improves the way you work. A great tool improves the way you think.


We'll go through a few different topics to help you make the best decision for you. If you have any questions or would like to discuss your requirements, just drop us a message!

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An Introduction to the ZOIC PalaeoTech Tools

The PRO Range

Each tool in the PRO Range is especially well suited to a particular job within fossil preparation, offering a significantly more refined user experience, quieter working and the lowest air consumption of any range in the world.


These tools are less likely to buck and have a more controlled stroke, allowing for more sensitivity and ‘feel’ for the work. The pusher-plate models (Microraptor and Velociraptor) have inbuilt Air Cushion Technology. The PRO Range tools are comfortable and ergonomic to use for long periods. It is our aim to provide you with a tool that makes you the best fossil preparator you can be. Whether performing mass matrix removal, or working under a microscope; these are fantastic tools.

THE entry-level air pen

The Trilobite offers an excellent entry-level option at a low price point. It was developed to provide an affordable air tool specifically suited to fossil preparation, as a graduation point from an electric engraver. Although not as powerful or refined as our ZOIC PalaeoTech professional range of pneumatic tools, the Trilobite is multipurpose, robust and precise.


The Trilobite is a modified version of a commercially available engraver (which unmodified is wholly unsuited to the job -read more below!), allowing us to produce it on a tighter budget than our handmade, bespoke air pens. We are able to pass on the benefits of these savings direct to the customer, along with all of our experience in what makes a fossil preparation tool useful, durable and great to work with.


What fossils are you prepping?

The internal mechanism of an air pen will dictate how successful you are at your prep. There are two types of air pen - which one suits your needs? All air pens in fossil preparation are variations of two different internal mechanisms. A very basic understanding of these internal mechanisms will arm you with the knowledge you need to make an informed choice. Often having one or more of each type of tool up your sleeve gives you the most flexibility in your set-up, but sometimes budget allows the choice of only one - so it's important to make the right choice!


Fossil preparation air scribes categorise into two general types. Whilst you may not need to understand how each type works, it makes a big difference depending on what you will be preparing and your successes with such. We call these types Impact Driven and Pusher Plate Driven. 


Impact Driven fossil preparation Air Pens

These are the powerhouses of the fossil preparation world. They are effective at speedy matrix removal even on hard rocks. They are often better with more pyritic or ‘stickier’ fossils, but less suited to working on anything fragile. The ZOIC PalaeoTech T-Rex air scribe has a reputation for its effectiveness on heavily pyritic rock, and this is why!

fossil preparation air scribe

How do they work? These function by the inflow of compressed air causing the repeated striking of a piston against the internal end of the stylus, controlled by balancing pressures in internal air galleries within the tool. It is a bit like striking an anvil with a hammer, many thousands of times per minute.


Below, see a diagrammatic explanation of how an impact-driven air scribe works.

fossil prepping air pen air scribe how work

With some of these impact-driven tools, like our ZPT T-Rex and ZPT ZOIC Chicago, as a result of the internal mechanisms they are much more powerful than their pusher plate counterparts and some are also able to work at much lower air pressures (low PSI) with considerably less air consumption. In fact, the low pressure tools (such as the ZPT-TR T-Rex) are significantly more powerful than their high pressure counterparts.


There are two main types of air pen within this category. Some have their optimum working pressure set much higher, and others work at very low pressures. This is a result of the size of the piston. At low input pressures, the pressure exerted on the surface area of the ZPT T-Rex is much greater than that exerted on that of the ZOIC Chicago (a modified Chicago Pneumatic CP-9361), because the surface area of the piston is significantly larger.


Low pressure tools (such as our ZPT-T Rex), funnily enough work at very low air pressures. They are quiet and economical to run; and require your air compressor to ‘kick in’ much less often. These tools have an optimum pressure range of 0.5-3.5Bar or 7-50PSI and are significantly more powerful for matrix removal. The frequency of the beats is also particularly effective when working on sticky fossils or pyritic rocks, generating microfractures causing ‘pops’ that would not otherwise occur.


Models like the The ZOIC Chicago are impact-driven and work at high pressures. These have an optimum operating pressure of 6.2 Bar or 90 PSI. This ZOIC Chicago is a good all-rounder that balances power and precision due to its size. A range of interchangeable styli are available. The ZOIC Chicago is fitted with our unique positive stylus locking mechanism, which means your chisel will never rotate or spin. Not once, not ever.


These tools are well suited to working quickly on harder matrix (all tools can work on hard matrix, but more patience is required with less powerful models). The downside of these tools is that they are less compatible with more fragile fossils as the force exerted is that much greater. They are usually too powerful to cope with delicate spines and other ornamentation on fossils where present.

  • Powerful matrix removal

  • Less noisy at lower pressures

  • Better with more robust fossils

  • Faster matrix removal

  • More likely to induce matrix 'popping'


pusher-plate driven fossil preparation Air Pens

These are best used for more delicate fossils and more detailed work, allowing reasonable speed of work with softer matrix. They also work well with harder matrix, but do not expect to be able to work quickly in terms of matrix removal. Ideally, you will not remove large amounts of matrix with this type of tool, but would typically use it once you have used an impact driven tool to remove overburden to get close to a delicate fossil (e.g. a spiny ammonite in a hard limestone nodule).

In the ZOIC PalaeoTech range, we call the pusher plate driven tools the ‘raptor’ series - the Velociraptor and the Microraptor. The Trilobite is also a pusher plate driven tool, operating on a simpler design.


How do these fossil preparation tools work? Compressed air enters the body of tool and builds up pressure against the pusher plate which is attached to the internal end of the stylus, and is sealed by rubber o-rings. When the pressure overcomes the spring force of the spring the stylus is pushed forward. The pressure is then released and vented through the exhausts, and the spring returns the pusher plate and stylus and o-rings back into their starting position many tens of thousands of times per minute. See the diagrams below:


This is a gentler action that the impact driven tools, as air is being used to push the stylus rather than the repeated tapping of metal on metal. They therefore remove less matrix at a time, and models with higher beats per minute (bpm) can act to pulverise the rock in their path rather than chipping the rock away giving you more control. They vibrate less enabling you to work with more delicate fossils, and the body of the tool is typically lighter because they are smaller.


Our pusher plate models include the all-rounder ZPT-VR The Velociraptor, and the ultra-precise ZPT-MR The Microraptor. The ZPT-TB The Trilobite is an entry level all-rounder model, designed to suit somebody that would like to start using air tools for fossil preparation without breaking the bank.

The internal o-rings do wear out (they’re seriously put to work!) and so they will need changing when worn. These tools are slightly higher maintenance in this respect than impact-driven tools but none of this maintenance is difficult or time consuming - we’re always here to help.


In our PRO Range, the Microraptor and Velociraptor have exceptionally frugal air consumption - the lowest of any range on the market. The Trilobite uses more air to run, cycling your compressor more often, but is still remarkably low when compared to commercial pneumatic engravers.

  • Perfect for detail and finishing work

  • Velociraptor (PRO Range) and Trilobite (Entry-Level) are all-rounders, suited to moderate matrix removal

  • Less vibration and more control on delicate fossils

  • Cheaper than impact-driven tools

  • Noiser (and higher pitched) than impact-driven tools


What's your budget?

Another thing to consider is your budget. Remember, if this is your first air pen, you will also need to purchase an air compressor and perhaps a water trap depending on humidity where you work as well as appropriate PPE. If you would rather buy an all in one to be sure of the costs up front, we do starter kits.


An ideal set up is one with a variety of air pens, often at different ends of the power spectrum, with the user gradually building up their collection over time. We have found that the combination of our T-Rex (powerful) and Microraptor (precision) is an absolute winner, allowing for some incredible prep work.


However, we appreciate that most people will only purchase one air pen to get them started. Usually, we would recommend one of our three all-rounder air pens that cover most bases. In our PRO Range, the ZOIC Chicago and the Velociraptor are excellent all-rounders, as well as the entry-level Trilobite. We offer both the ZOIC Chicago and the Trilobite as part of a starter kit, with the compressor, safety glasses, dust mask and all the fittings required. 


The ZOIC ChicagoVelociraptor and Trilobite are all-rounders. We would normally recommend the ZOIC Chicago if you are working on harder rocks with less fragile fossils, and the Velociraptor for softer rocks with more fragile fossils. The Velociraptor is capable of a greater degree of delicacy and detail. This is not to say that it doesn’t work on harder rocks, just that it will be a slower job in terms of matrix removal because it is not as powerful. However, this gentler action is eminently suited to fossils that could be easily damaged by a more powerful tool. The Velociraptor also has a wider working pressure range than the ZOIC Chicago allowing to be more flexibly applied to different jobs on the detailed end of the spectrum. For most British rocks, if you are to only have one air pen, the ZOIC Chicago is the most appropriate. As you grow your kit, you can complement it with either the Microraptor for more precision, or the T-Rex for more power. 


If you are on a much tighter budget, or simply can’t necessarily justify the expenditure on a hobby you can only make a little time for then the Trilobite is perfect for you. The Trilobite is an affordable air pen perfect for the beginner. It is mid-powered, but also capable of fine work with its adjustable pressure input. It is an enormous leap up from working with an electric engraver. 


what to look for when choosing an air pen

When choosing, there are a few physical things to look out for in both new and second hand fossil preparation air pens or air scribes. A quality tool will last you many years (even decades) when looked after. These following bits of advice apply when choosing a new or a second hand tool – naturally a second hand tool will show wear and tear more obviously than a new one, but there are a few indications of how a tool might hold up over the years. 


How well suited is the tool to fossil preparation?

The first major thing to think about is how appropriate the tool you're looking at is for fossil preparation. Bear in mind that not all air scribes are suitable for fossil preparation. Fossil preparation tools are typically designed specifically for that purpose, or modified from mass-produced pneumatic metal/plastic etchers and engravers. 

Pneumatic Engravers - the good, the bad and the ugly.

If you see a metal engraver or air scribe for sale, don’t just assume that it will do the job just fine. Unfortunately some mass produced engravers are misleadingly marketed as fossil preparation tools when they are not fit for use.


Unmodified, or non-purpose built air scribes will likely have some things in common:

  • Metal-working tungsten carbide. We use stone-grade tungsten carbide in all of our tools, which withstands the abrasive nature of rock for longer and requires less sharpening. 
  • Unhardened or slightly hardened stylus bushing. Pneumatic engravers or air scribes for metal/plastic engraving don't require a hardened bushing, so they often don't have this. This means that after not much use, the stylus begins to wobble. Just because it's metal, doesn't mean that it won't wear over time. It needs to be properly treated for durability. 

  • Short, stubby stylus. A longer, more slender stylus and supportive bushing are recommended for working with rocks.

The ergonomics, extended reach of stylus and enhanced resistance to wear and tear make a purpose-built fossil preparation air scribe a better choice. Fossil preparation is a demanding activity on any tool, and you need to be sure that you're investing in one that is up to the job. 

A rundown of some popular air scribes or pneumatic engravers - do they have a place in the fossil preparation workshop?

You may have seen some of these for sale and been curious. We'll run through some of the characteristics of these mass-produced engravers to give you an idea of whether they might have a place in your workshop.


What may seem cheap, may end up costing you in terms of needing to replace a tool after very little use. Spares for these tools often aren't cheap, nor available in some cases. Many of these engravers (air scribes, air pens, air incisors) have extremely high air consumption, either meaning a very large compressor is required, or you will burn through compressors at a pace (all whilst clocking up a high electricity bill). There are many variables to consider, and fossil preparation is a very demanding activity. 


Some of these tools are well made and very good at their intended application in their intended industries, but most are poorly suited to fossil prep. If you've somehow ended up here and you're just looking for information about various engravers you will find more helpful advice in forums and reviews from other people in your industry. These are not general reviews and whether an engraver is suitable for fossil cleaning or not does not have any reflection nor bearing on whether it is suited to its intended purpose. Chicago Pneumatic and Sealey in particular are market leaders for their air tools in their respective fields and applications with good reason.


Fossil Preparation Rating

The CP-9361 (Chicago Pneumatic)

The most famous pneumatic engraver of all is the CP-9361, which was almost ubiquitously used for fossil preparation until better, more appropriate tooling came along. As a metal/plastic engraver, it's brilliant.


Many preparators still choose to use an unmodified CP-9361, but a longer, more slender stylus and more supportive bushing are recommended for working with rocks. The ergonomics, extended reach of nib and enhanced resistance to wear and tear make a modified version a better option.


The internal workings are the real star in this tool. They are exceptionally durable and some have been going for 20+ years. We use the CP-9361 engraver as the base model of our ZOIC Chicago, utilising the power and durability of the internals, whilst making the external components suitable for fossil preparation. 


We offer a modification kit to convert the CP-9361 into a ZOIC Chicago. 


Our verdict:

  • It's OK for fossil preparation, but not ideal

  • Don't be lulled into thinking the CP-9361 Industrial Engraving Kit in the red box (as here) comes with a set of chisels. They are steel scalers and won't last any time at all for fossil prep.

  • Can be converted into a ZOIC Chicago with a modification kit if you find one going second hand at a good price

  • For just a little bit more money, you can purchase a brand new ZOIC Chicago that will last much longer, takes a point and a chisel and is better suited to fossil preparation.

  • Beware knock-offs, of which there are many.

Fossil Preparation Rating

The CP-9160 (Chicago Pneumatic)

The CP-9160 is a light-duty metal and plastic engraver designed as a cheap product for small, quick engraving jobs which it excels at.


It is unsuited to fossil preparation and doesn't tick many boxes in terms of comfort or demands on the air compressor. 


It is extremely air hungry, using a whopping 1.69 CFM (nearly 50 litres per minute). To put this in perspective, this is almost 8x the consumption of our ZOIC Chicago.  This means it requires a 1.5kW (2HP), 50l (13 gallon) air compressor minimum (much larger if silent). You run up your electricity bills no end, but you also risk burning out the compressor motor if your compressor is undersized or underpowered for the tool. 


It is comparable in power to the Trilobite, but the Trilobite is more comfortable to use, significantly more durable, and costs only a bit more. It will stand the test of time for fossil preparation, where the CP-9160 will not. 


Our verdict:

  • AVOID for fossil preparation. Don't be tempted by the low price. 

  • Very air hungry - you will need a hefty compressor to handle one of these.
  • Chicago Pneumatic designed this for short bursts of work, rather than the hours of fossil preparation we all want to be doing! The phrase 'light-duty' says it all.

  • No frontal exhaust.

Fossil Preparation Rating

Sealey SA96 Air Engraver

The Sealey SA96 is another light duty engraver designed for marking tools, components and security marking loan products. It is intended for perhaps a few minutes use at a time. For their intended application, they are well made tools at a good price.


For fossil preparation, it is a long way from what you need. It is very 'weak', with almost no power for matrix removal. It also doesn't have the delicacy required for very fine work. 


It has an internal cylinder and piston, which means that it's an impact-driven tool, but lacks the power required to do the job. It is in fact less powerful than our Microraptor, which is also more appropriate for fine, detailed work as it imparts less vibration to the fossil. 


The air consumption is an enormous 4 CFM at 60PSI (114 litres per minute at 4.1 Bar). We wouldn't run this tool continuously off anything short of a 100l, 2.2kW (26+ gallon, 3 HP) belt-driven air compressor. Electricity bills will be extremely high, for very little result.


Our verdict:

  • Avoid for fossil preparation. Will not last and doesn't do much for matrix removal. Needs a large, industrial compressor to run continuously.

  • A spare stylus will set you back almost as much as the tool again.

  • Too weak to remove matrix, too many vibrations to prep delicate fossils

  • Air consumption is through the roof - we wouldn't run this continuously on anything less than a 100l belt-driven air compressor. Would run fine on a smaller one, if only used for 1-2 minutes at a time as intended. 

Fossil Preparation Rating

Various cheap 'copies' of the CP-9361

The Chicago Pneumatic CP-9361 is such a popular model that it has inspired a plethora of cheap knock-offs and counterfeits. These only last a matter of weeks (months if you're lucky). Some literally fell apart in the users hands. 


You may see some with elongated styli, making them look suited to fossil prep - which they are not. They aren't suited to engraving, let alone a more strenuous activity. Impact-driven tools and engravers are the most difficult to manufacture engineering-wise, with a lot of room for error. They are also typically not CE or UKCA certified and therefore not only considered dangerous, but illegal to sell in the EEA and the UK (doesn't stop them trying!). 


A few ways you can spot a knock-off:

1. The price! If it's too good to be true, it probably is. 

2. High air consumption - these often have a 2CFM (60lpm) air consumption. The original CP-9361 uses 10x less at 0.2 CFM (6lpm). Some are advertised to use the same as the original CP, but in reality use far more air when you actually have them.

3. The operating pressure. Sometimes recommended at 60 PSI (4 Bars) - this is due to the poorly made internals. The piston will likely have trouble moving freely inside the cylinder, frequently 'sticking'. 


Our verdict:

  • Avoid altogether. Don't be tempted by the low price.

  • Will not last any time at all. May seem cheap but an expensive mistake. So poorly made they are not repairable. 
  • May be sold under a variety of brand names for a variety of applications. 

Fossil Preparation Rating

Generic (sometimes branded) pusher-plate Engravers

This one might look a little familiar! There are numerous mass-produced pusher plate engravers out there more or less replicating the ARO which was popular in fossil preparation many years ago, again before the advent of more advanced tools. The shape and the knurl are very distinctive so you should be able to spot one of these a mile off. 


We actually use a better quality version of one of these tools as the base model for our Trilobite Air Pen, which is one reason we can make it so affordable! Ours has, however, been fully overhauled for fossil prep. These air scribes are made in many factories worldwide and many companies label them with their own branding. They do vary in quality from place to place quite considerably, but being pusher plate tools the room for error is less than with impact-driven tools. 


However, once again we face the problem that they are not durable in fossil preparation. The stylus bushing (the 'nose' of the pen) is very rarely hardened in these unmodified versions, and metal can wear very quickly. This causes the stylus to increasingly wobble about with a sloppy fit, making any accuracy very difficult. They are also very noisy, air hungry (often around the 2CFM mark), and don't have a frontal exhaust meaning that the dust will sit on your work. 


We've stripped the unmodified version of all the features that render it not durable and unsuitable for fossil preparation. The Trilobite is a much improved version. It is much quieter, has an optional and interchangeable frontal exhaust (and so is more flexible for work with fragile fossils and matrix removal) and a stylus bushing that means you won't see any wobble for years. We also reduce the air consumption and provide a better 'feel' for the work. Our Trilobite is fitted with stone-grade tungsten carbide, rather than the metal grade found in the unmodified versions. 


Our verdict:

  • It's OK, but for only a bit extra you can purchase the Trilobite which is fully kitted out for fossil prep.

  • Unmodified and/or lower quality versions won't last long. Spares are difficult to get.
  • May be sold under a variety of brand names for a variety of applications. 
  • Air hungry. 2 CFM is demanding and will require a reasonably sized compressor for continuous use.

CHOOSING A SECOND HAND AIR PEN - SOME THINGS TO LOOK OUT FOR

Perhaps if you're looking at getting one of the above pneumatic metal/plastic engravers, maybe avoid. There are also things to watch out for in 'purpose-built' tools. Consider how much use the tool has had and how much life it might have left. Can you get hold of spares easily? Will you be able to get spares and have it serviced in the years to come?


One of the main things to watch out for and a sign of either poor build quality or a very very used tool (or usually both) is a wobbly stylus. The stylus should not wobble in the bushing – when this happens, more kinetic energy (power) is lost from side to side and not fully directed forwards. It is also harder to use a wobbly stylus as you can never be too sure where it is going to end up, on the rock or on the precious fossil!


If the bushing hasn't been sufficiently hardened during the manufacturing process, the stylus will develop a bit of personality. Our tools are all made to have a precision fit between stylus and bushing, so that maximum power is transmitted forwards and allows for maximum control. We harden and temper the metal (you can see that the bushings in the ZOIC Chicago, Microraptor, Velociraptor and the Trilobite are either a bluey or yellow colour – a side effect of this process - the T-Rex bushing is internal!), so that it will last you donkey’s years even with the heaviest use. Although side-to-side motions are not recommended for longevity of your tool, we understand that this is one of the easiest ways to smooth matrix. Our products are built to stand up to this movement for many years.

second hand fossil prep tools air scribe air pen

Another factor to pay attention to is air consumption. Not only does a lower air consumption mean that the tool is cheaper to run (running off a smaller, cheaper compressor, and allowing for the compressor to kick in less) but can also be an indication of manufacturing quality. Air consumption is dictated by the style of internal mechanism to a certain extent, but within a line up of comparable tools, the lowest air consumption for the internal mechanism means that there is less space within for air to be ‘wasted’ and escape. The tighter the engineering tolerances, the lower the air consumption. We pride ourselves in quality of workmanship and our range has the lowest average air consumption on the market. For example, the T-Rex, running at 5lpm (0.17 CFM) might only cycle a 50l compressor once every half an hour. 


CONGRATULATIONS!


You've stuck with us this far! We very much hope that this guide has been helpful. It's important to understand some of the technicalities of how these tools work, in order to get them to work their best for you.


We find that the best results are achieved by using a range of air pens, but obviously this is not appropriate for all budgets. If you are getting one at a time, it's best to for an all-rounder, and then complement it with the most opposite tools (i.e. more power, more precision). The rule of opposites means you've got all corners covered!


In our PRO Range, the ZPT-CP ZOIC Chicago and the ZPT-VR Velociraptor are great standalone tools; the Chicago for fossils in harder matrix, and the Velociraptor for more fragile fossils. The T-Rex is a great all-rounder and very versatile with its range of nibs, but is best for more sturdy fossils in harder rocks. The Microraptor is perfect for really fine and delicate work. Many of our customers find that their most frequently used combination are their T-Rex and Microraptor which will suit most jobs!


The Trilobite is a budget friendly, entry-level air pen designed to make fossil preparation using pneumatic tools more accessible to more people.