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Making Micarta scale material

Since many of members of SRP expressed an interest in Micarta as a material from which to make razor scales, ignatz has made time to properly document and illustrate the process.

Contents

What is Micarta?

Micarta is really nothing more than a composite of cloth or paper in glue. Long ago, the material was originally made with phenolic glue, but for our purposes epoxy resin is more convenient. Almost any cloth should work, although my preference is for simple woven cloth from natural fibers such as cotton, linen or silk. In the writer's opinion, stretch fabrics are probably less interesting as they might contribute to the finished Micarta sheet being somewhat too flexible. The reason for choosing a cloth made from natural fibres is simply from a fear that some sort of chemical reaction between the epoxy resin and synthetic fibers could end up making for a weak result. Another cloth material that could be used is fibreglass. Structurally it is excellent and is totally compatible with epoxy resins. On the other hand, fiberglass is not necessarily so very pretty for the purpose of making decorative razor scales.

Paper may also be used within the composite, but one must take care that the paper is sufficiently porous to fully absorb whatever resin you use. If you chose to use some paper with a plasticized upper surface (inkjet photo papers, for example) it is possible that the plasticized surface would not allow the resin to permeate sufficiently and that the resulting piece of Micarta might later come apart, shearing along the (insufficiently impregnated) inner paper surface. This is definitely not desired.

Do be aware that cloth or paper will no longer appear the same once drenched in resin. This is somewhat akin to the way that clothing changes appearance when wet. Most usually, colours become darker and somewhat less brilliant. Additionally, some measure of opacity is lost. Paper, even more so than cloth, may take on a very different look when wet than when in the normal dry condition. The rule is: If there is any doubt, experiment on a small sample first before committing your time and materials to a finished product.

Choosing the right epoxy resin

We are choosing for epoxy resin as the glue to bind our Micarta. However, there are many epoxy formulations and not all of them are equally suited to our purposes:

  • The correct epoxy should first and foremost have a slow set and a relatively long working time.
  • The working time is that amount of time between first mixing the resin components together and when the mixture starts to gel (thicken). An epoxy resin with a long working time is what we want, since we are going to carefully apply it to each layer of cloth in our lay-up.
  • The setting time (also known as the curing time) is that amount of time it takes the resin to harden to the point where it can be safely handled and/or used. In general, an epoxy with a long working time will have a long setting time. Do please note that once the usual setting time has elapsed your epoxy will have a reasonable hardness, but that in some cases the absolute hardness of the epoxy resin will only be reached after some additional time has passed (hours or even days). This varies from epoxy to epoxy and so one will want to consult the technical information sheet for the particular formulation one is using.

We are also looking for an epoxy which does not exhibit a strong color influence on the final result. Again, in this regard, not all epoxy formulations are the same. For many industrial purposes, color and or transparency may be of no importance at all when compared to other more important qualities such as strength, water resistance, heat resistance and so on.

The epoxy formulation that was found for this demonstration is rather good in all the aspects that pertain to the hand lay-up of Micarta sheets. This epoxy formulation is intended for pour-surfacing of floors and table tops. Although each of the two components has a bit of color on its own, when mixed together they become water clear. The working time is something like twenty to twenty-five minutes (20-25 minutes) and the setting time is about twenty-four hours (24 hours). During the working time, the consistency of the mixture begins by being only slightly thicker than milk, becoming rather more like syrup near the end of the working time. As a final benefit, this epoxy formulation has the quality of filtering out UV rays. This should offer a measure of additional protection against color aging of any cloth or paper within the matrix of the finished Micarta.

A few words about temperature

A few words about temperature are in order at this point. A minimum amount of heat is a requirement for epoxy resins to set. Most curing times (setting times) are expressed as the amount of time required for the mixture to harden when at room temperature (20°C = 68°F). If one lowers the room temperature, the setting time will be increased. Lower the temperature too much and the required chemical reaction will slow to the point where the epoxy will fail to cure. Extra heat (increased temperature), on the other hand, will accelerate the chemical reaction, thus reducing the setting time.

The chemical reaction that enables Epoxy resins to harden is exothermic. ‘Exothermic’ is a fancy way of saying that the chemical reaction generates heat. The larger the mass of the curing epoxy, the more heat that tends to collect. And, since increased heat tends to generally accelerate the setting time of epoxy, it can be that both the working time and the setting time will be reduced if that heat is allowed to build up. Some hobbyists have reported this effect when mixing up large batches of resin. In practical terms this can mean that the rate of hardening can accelerate such that the mixture hardens while you are still trying to apply it. In the small amounts and the thin layerings of epoxy which we will be using for creating scale material this should not be a problem. Just remember to stay away from the extremes of heat and cold when using epoxy resins.

Some of you may be interested in knowing exactly which epoxy was chosen for this demonstration and why. This mix is simply called Epoxy RP 025 UV, distributed by a company called Assyst, located in Mechelen, Belgium. As previously stated, it is actually intended as a poured floor covering, but it was purchased at a local art supply store where it was actually sold for use in making epoxy-encased objects (flowers in epoxy cubes and that sort of thing). It was not initially known if this epoxy formulation would serve for the intended purpose of making Micarta sheet until it was tried, but it ended up giving very satisfactory results. If you are reading this from somewhere close to the writer's area (Belgium), then you might wish to visit the Assyst web pages (Dutch & French language) to check up on what they offer: http//www.assist.org

A great many of you are reading this in other parts of the world and will not be able to find the same epoxy formulation that was used in this demonstration. Unfortunately, the writer cannot give any reliable advice concerning either epoxies or suppliers of same outside of this area. If you decide you wish to try your hand at making Micarta then you will have to look around and make your own best decisions regarding which epoxy to buy and where.

A cautionary note on safety

Remember to wear disposable gloves

A cautionary note on safety using epoxy would be in order.

  1. Be aware of possible fumes from the epoxy resin. These fumes could come from either the resin or the hardener in the uncombined liquid state as well as the possibility of fumes emanating from the epoxy mix while it cures. Whatever epoxy formulation you choose to use, you can assume that breathing the stuff is not healthy. So proper ventilation of your workplace is just a very good idea, but strongly recommended.
  2. Likewise, keep those hands clean. Epoxy resins are not biologically friendly and induce allergic skin reactions in some people, so try to avoid direct contact whenever possible. See those disposable gloves in the photo? Get some for yourself and use them.
  3. Finally, do please try to dispose of any leftover resin in a responsible manner. Respect our environment.

Choosing the right cloth

Materials used in this tutorial

Cloth is much simpler to get your hands on. Take a trip to your local sewing supplies center and purchase a few half meters of some colored, cotton cloth. But it is just as simple to grab an old pair of blue jeans or other colorful bits of cast off clothing.

The cloth used in the demonstration measures as 0.25 mm thick for both the yellow and orange cloth, while the cream measures 0.45 mm in thickness. The seven layers of cloth – 2 yellow, 2 orange & 3 cream – give a total measured thickness of 2.2 mm when dry. Depending on the epoxy fill and the clamping pressure, the actual thickness of the finished Micarta may end up being slightly more or very slightly less.

Using a brush effectively

Tying off the brush with some string or carpet thread

Applying the epoxy will require a brush. Whatever brush you decide to use, it will end up as a one-time throw-away. This would suggest that a cheap brush would make the most sense. Some of you use those little metal-handled brushes meant for the application of glue or acids. Not finding a source for them in this area, an alternative was found in some inexpensive paint brushes which come in a kit of four of five together.

The brush in the picture has two faults. First of all, it is somewhat larger than desired for this purpose. That means it will suck up a greater portion of that valuable epoxy resin (waste). Second of all, cheap brushes often tend to be badly glued so that they shed hairs… right into the work. This is definitely not cool.

A simple solution to both of those problems is to tie off the brush with some string or carpet thread. This effectively shortens the brush, reducing the amount of resin it will suck up. Additionally, this stabilizes and holds the hair very tightly. We can add to the effect by putting a few drops of super glue onto the brush hairs above the tied-off portion.

Making Micarta scale material, step by step

Now there isn’t much mystery about the actual mechanics of making Micarta. At its simplest it is resin-impregnated material which is pressed together. There are some fancy ways of doing this using hydraulic presses or vacuum bag outfits, but since most of us have more modest budgets, we will be applying pressure to the Micarta with simple wood clamps. The writer has seen others who used two, flat pieces of wood for the purpose of pressing the Micarta. Our approach is slightly different in that while a piece of wood will serve as the top half of the press, the bottom half of the press will be a thick slab of stone. Since stone does not bend, it guarantees that at least one surface of the finished Micarta is properly flat. By the way, that is a slab of Belgian Blue Stone. The better grades are sometimes used for inexpensive hones, but around here in Belgium it mostly serves for door thresholds, floor tiles and window ledges. It is so common that people throw away used bits of it without a second thought.

A stone slab with some of the components used in this tutorial on top of it

The stone is supported on two blocks of wood so that the wood clamps used to apply the pressure will have some clearance away from the table top. On top of the stone you can see a sheet of paper. This is a special sort of silicon treated baking paper which is intended for use in the kitchen (cookies, bread, etc.). It is heat resistant and nothing sticks to it at all, so it is the ideal stuff to keep our epoxy-drenched Micarta lay-up from sticking to the stone. On the top of the lay-up stack will come a second piece of this silicon-treated paper baking paper, this time to separate the lay-up from that top slab of wood on which the clamps are exerting their force. Standing on top of it all are parts A and B of the epoxy (resin and hardener). Most usually, epoxies are so formulated that one mixes equal portions of both components to obtain the working resin mix, but in this case the ratio is 2 parts resin to 1 part hardener. Again, read the instructions for your own epoxy very carefully.

OK, let’s dive in and start the lay-up procedure.

The economics

Now that the process has been explained and illustrated from start to finish, some of you may be wondering about the economics of making your own Micarta. Let’s tote this up, starting with the materials.

Cloth 
The cloth is the big unknown. Either you buy it new from the store, or else you raid the rag bag for some fine cast-offs. We will arbitrarily set the cost of the cloth actually used at no more than 2 euro.
Epoxy 
Epoxy-wise; we used 45 ml of parts A & B together to make this particular sheet of Micarta. The epoxy was originally purchased in two bottles having a collective volume of 1500 ml at a cost of approximately 53 euro ($75 at current exchange rates). Doing a quick bit of math, our figures show we can make perhaps 30 pieces of Micarta of similar size using the resin at this rate. And that would put the cost of resin per pair of Micarta scales at about 1.75 euro ($2.50).
Paraphernalia 
Then there is the cost of a disposable brush and disposable gloves, plastic mixing container and a couple of sheets of that silicon treated baking paper. We’ll add in 1.25 euro for all these things together.

That brings our actual material costs to around 5€ (about $7.15).

Finally, we have the actual time spent on doing the cloth cutting, lay-up and clamping. The whole demonstration took about four hours. But only about twenty-five minutes of that was the actual lay-up. Most of that time went into preparation in the form of collecting and preparing the tools and materials as well as documenting the process and setting up the camera and taking pictures. Normally, one should be able to get this all done in slightly more than an hour. So we can throw in the charge for one hour of work on top of our material costs. All things considered, this would make the cost for creating one’s own custom Micarta scale material very reasonable.

Also keep in mind that for the purposes of this demonstration we have kept the Micarta fairly simple, but there is no reason why you cannot explore all sorts of special creative options. You can fold the cloth, weave it together or twist it. You can also embed such things as colored threads, string or even small bits of metal or wire. You can also add coloring materials to the epoxy (!). Feel free to experiment and enjoy yourself.

And now to start working on a set of scales. But that is best left for another article. ;)

Acknowledgements

This article is based on original work by Ignatz[1]

See also

References

[1]<http://straightrazorplace.com/workshop/40286-making-micarta-scale-material.html />


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