Paper’s Effect on Fountain Pen Line Widths

I have noticed that when I’m writing scratch notes on the back side of waste printer paper with my fountain pen I get blobby lines. It usually feels difficult to write clearly, especially when I scribe crossing paths in a (pointless) attempt to clarify my handwriting mistakes. Of course there are many variables at play in writing, but I was curious about why it seems particularly crummy in the common case of scratch paper.

This post looks at realized line widths for the same pen, the same ink, on three kinds of paper. My working mental model is that a wide line makes writing more blurred and blobby, and therefore harder to read.

Results

Properly designed notebook paper is smooth and less toothy. Line widths on notebook paper are 10% narrower and have very consistent width. It is probably also sized with treatments that limit the absorption of the ink. The archival paper seems also to be sized causing the ink to stand proud of the paper; on the other hand it is about as rough as the copy paper causing a wider line with feathering.

Paper Mean Width Width Std Dev
Copy 0.547 mm 0.0087 mm
Archive 0.546 mm 0.021 mm
Notebook 0.500 mm 0.00057 mm

The standard deviations are based on three measurements each, so are not brilliantly reliable. However, the significant smoothness and narrowness of the notebook sample are consistent with eyeball observation.

Measurement Conditions

Ink is Pilot Iroshizuku in the Yama-budo color, a beautiful magenta-purple ink. This ink is very liquid, even runny, compared to an ink like Rohrer & Klingner Schreibtinte document ink. The latter is waterproof, but is acidic and corrosive to pens in addition to smelling bad.

I tested on three kinds of paper:

  1. Copy paper is generic a generic printer or laser copier paper.
  2. Archival paper is Southworth Business 25% cotton 20 lb. (75 grams/square meter) and is listed as acid and lignin free.
  3. Notebook paper is from an Oxford Black n’ Red notebook. The lines are qualitatively similar to those from an Oxford Signature Journal.

The pen is a cheap knock-off of a TWSBI with an EF nib. The nib came with the pen, but is not made by the cheap-o producer. I believe it is a rhodium-plated steel.

Data and Results

I drew a set of lines on samples of the paper. Notice, in the following figure, that the journal paper smeared–this did not corrupt my results but it illustrates a common problem I have with this writing.

Scan of samples.

Zooming in to the practical limits of my scanner shows the same three samples in a different order. Notice how uniform the journal paper’s line is (at right), and how feathered the archive and copy paper are (center).

Zoom-in on all three line samples. Left-to-right, copy paper, archival paper, notebook.

To get a more accurate measurement I put the samples under the microscope with a calibration slide on top to get the absolute scale. All photos use the same oblique bright-field lighting. The line looks shiny on the copy and archive paper, though much more so on the archive paper. The line on the notebook sample is very consistent and flat.

I measured each line’s width at three arbitrary places transverse to the line. These three measurements are summarized in the first table. With only three measurements the numerical utility of the standard deviation is questionable; however, simple inspection shows that the notebook has a more consistent line width with smaller feather features. That is followed by the archive paper line, with the copy paper bringing up the rear with bad feathering.

Micrograph of ink line on copy paper. 1 div = 0.1 mm.
Micrograph of ink line on archival paper. 1 div = 0.1 mm.
Micrograph of ink line on notebook paper. 1 div = 0.1 mm.

Direct Monitoring Amplifier

I like to use closed headphones. These often significantly attenuate outside noise but challenge me to hear my own voice. Typical attenuation of some relevant headphones or headsets are summarized by the following table.

Headphone Attenuation
Westone in-ear Monitors 23 dB
Audio Technica ATH-M50 11 dB
Hyper-X Cloud II 16 dB

I want to use these headphones  along with an external mic or headset with my mobile phone or, in the age of COVID, with my computer when telecommuting. My children, in online education, are faced with the same need but have less flexibility about what equipment to use since they have district-issued Chromebook devices.

I want direct monitoring, where I can hear my voice combined with the signal from the computer. If you have used a plain old land line phone, then you have experienced direct monitoring of your own voice.

This article is about a circuit that solves the problem by allowing the user to plug his or her headset into the circuit then plug that circuit into the computer or mobile phone. A number of solutions other than this circuit exist but have substantial shortcomings:

  • Open headphones, like the Koss Porta Pro allow you to hear your own voice but also hear all the other telecommuting members of your family
  • USB sound devices with built-in monitoring and appropriate microphone inputs are rare. I use ATH-M50 headphones and an external dynamic microphone with Focusrite Scarlett Solo and it is excellent. Using it with a headset like the HyperX Cloud II requires stepping down the mic’s phantom voltage with a device like the Rode VXLR+. For a computer this functions excellently, but has drawbacks. It does not work with a phone, it is bulky on the kids’ work surfaces (kitchen table), and costs a lot.

My solution is the a custom circuit packed into a hand-painted Altoids tin, shown in the following picture.

20201224-091647-03
Photo of the completed project. C plugs into the computer or phone, H plugs into the headset.

I designed this project to the objectives:

  • Plug in a headset and a computer or phone (3.5 mm TRRS Android/Chromebook wiring, as opposed to Apple)
  • Wearer can hear himself or herself speaking in the headphones, with no delay or latency
  • Wearer can hear the sound from the computer or phone
  • The computer or phone receives the signal from the microphone normally

The following figure shows architecture of the adopted basic design. A preamplification stage provides a low noise transimpedance amplifier for the microphone signal. This signal is supplied to the computer or phone. The signal is also passed through a user-controlled variable gain stage that lets the user adjust the volume of his or her voice without changing the signal strength provided to the computer or phone. The final two amplifiers are adders (audio mixer circuits). These combine the mono microphone signal independently with the left and right stereo outputs from the computer or phone.

Basic architecture of the circuit

Finally, I want the circuit to be powered either by a reasonable battery stack consisting of a modest number of inexpensive batteries like AAA or AA or by the USB 5 V supply. USB supplies are often quite noisy and would require at least USB-OTG to work with a phone, so I assumed and implemented battery power for this design.

This report discusses the design of each stage of the circuit in basic architecture figure. The section Signal Analysis analyzes the circuit mainly through simulation results. Finally, the Discussion section covers future directions to take with this circuit.

Preamplifier Design

The preamplifier stage is the most sensitive element of the design. It must be low noise, and correctly bias the microphone. It does not need much gain since the computer or phone are designed to work with the same voltages the electret microphone produces. I followed the design process laid out in the article Single-Supply, Electret Microphone Pre-Amplifier Reference Design by John Caldwell, of Texas Instruments. Designing to a cut-off frequency of around 20 kHz resulted in the design shown by the following figure.

Pre-amplifier circuit design. The boxed section on the lower left is not part of the actual circuit, but is used for simulating the mic. The voltage supply is 6.2 V corresponding to four alkaline AAA batteries in series. Also note that capacitor $C_2$ is, per Caldwell’s recommendation, a film capacitor–Mylar in my case.

Capacitor $C_2$ is a film capacitor because the voltages are high enough that high-K ceramic capacitors will induce distortion in the signal because their capacitance changes depending on their voltage. Capacitor $C_3$ and $C_5$ AC-couple the circuit to the microphone capsule and to the computer or phone. $R_6$ prevents charge accumulation on $C_5$ which helps prevent a rapid large discharge into the computer.

Between the coupling capacitors is an op-amp transimpedance inverting amplifier. The op-amp used for this is a low-noise, low voltage, rail-to-rail design. I had some OPA4228 chips already, and although there may be better parts like OPA172 or OPAx227 with its unity gain stability, this worked extremely well in a breadboard experiment.

The current from the microphone $i = 16.17$ μA, and we are seeking an output voltage of $V = 100$ mV. These together set the feedback resistor $R_2 = V/i = 6.8$ kΩ.

We need to bias the microphone with $R_1$. The bias voltage on the mic should be $V_{\text{mic}} = 2$ V and we expect a small current through the microphone of about $i = 0.5$ mA. With a $V_{cc} = 5$ V supply,
$$
R_1 = \frac{v_{\text{cc}} – v_{\text{mic}}}{i_{\text{s}}} \approx 5.6\mbox{ kΩ}.
$$
It would also be reasonable to set $R_1 = 6.2$ kΩ, but breadboard experimentation later showed a slight perceived audio preference for the smaller value.

The feedback capacitor $C_2$ creates a single pole filter with $R_2$. Allowing for 0.1 dB ripple in the passband derives a constant 0.989 for calculating the pole frequency $f_p$ from the cutoff frequency $f$ as
$$
f_p = \frac{f}{\sqrt{0.989^{-2} – 1}} \approx 134\mbox{ kHz.}
$$

The cutoff frequency for voice audio is almost certainly less than 20 kHz, but it is reasonable to design to that. Then
$$
C_2 = \frac{1}{2πR_2f_p} \approx 192\mbox{ pF}
$$
assuming $R_2=6.2$ kΩ.

The low-frequency response of the circuit ticks up, a behavior that is inaudible here and can be adjusted by changing the coupling capacitor C3 provided instrumentation is available. In practice it was not terribly important.

Mic Gain Stage

The gain stage schematic in the following figure shows a simple inverting amplifier with gain between 0 and $100\mbox{ kΩ}/20\mbox{ kΩ}=5$. In hindsight we could have used a smaller variable resistor along with a smaller input resistor. The input resistor was chosen after some experimentation, a 10 kΩ resistor was too small, leading to touchy control.

Gain stage circuit. The variable resistor is from 0 to 100 kΩ. This op-amp’s positive input is tied to the same voltage $V_{\text{B}}$) as used by the preamp so the negative input can be DC-coupled with the preamp’s output.Gain stage circuit. The variable resistor is from 0 to 100 kΩ. This op-amp’s positive input is tied to the same voltage ($V$_{\text{B}}$) as used by the preamp so the negative input can be DC-coupled with the preamp’s output.

Mixer (Adder) Stage

The final stage is an audio mixer, it is two identical channels each with a separate input resistor for the mic signal and for the computer signal. The gain is fixed, as is the relationship between the mic and computer source gains.

Generic adder (audio mixer) circuit

In the generic mixer circuit, the output due to the input $V_1$ is
$$
V_{\text{out}} = -\frac{R_f}{R_1}V_1,
$$
it is negated as expected of an inverting amplifier. All the inputs are combined and negated, so that
$$
V_{\text{out}} =
-\left(
\frac{R_f}{R_1}V_1 +
\frac{R_f}{R_2}V_2 +
\frac{R_f}{R_3}V_3
\right)
$$
is the output–the sum of the inputs negated. In the circuit design we actually have an attenuation in the mixer channel, with $R_f/R_{\text{in}} = 5.6\mbox{ kΩ}/10\mbox{ kΩ} = 0.56$. There is some liberty in setting the gain of this stage, a dual-pull potentiometer is large and to be avoided. In later breadboard experimentation we changed this to a unity-gain circuit and appreciated the consistent computer output that gave us.

Mixer stage schematic. A voltage source represents the signal from the computer for simulation. This is AC-coupled through a 10 kΩ resistor into the inverting configuration of the amplifier. A relatively large 470 μF capacitor AC-couples the headphone cable–mainly intended to keep the circuit output from pulling down to ground. The 32 Ω resistor represents the headphone coil itself for simulation.

Signal Analysis

Oscilloscope inspection of the microphone preamp stage showed gain is proportional to frequency, as expected. Additionally, oscilloscope inspection revealed the expected voltage gains (inverting) including the poorly chosen fractional gain of the mixer stage.

A protoboard with vias instead of trace supports the circuit. Makes a congested and ugly product.

Most of the important frequency modeling is about ensuring reasonably flat response of amplifiers over the passband. The following power spectral density plots show that this is reasonably well achieved. Breadboard experiments have selected slightly more optimal values for capacitors in terms of how things actually sound, but the curves remain fairly similar. Slightly more suppression at low frequencies, and slightly less at high frequencies.

Gain design (top) and actual implementation (bottom). Notice that the actual implementation starts to roll off above 10 kHz–this reduces noise with no noticeable loss of fidelity.

Discussion

The design presented here should certainly be modified:

  • The gain of the mixer stage should be unity. This would make the response of the circuit to the computer’s or phone’s volume control work nicely. Unity gain helped in breadboard trials since the boxed version was assembled.
  • Assessment of the output with an oscilloscope showed a strange instability. When the variable gain is set approximately mid-range the circuit shows an abundance of high frequency whitish noise. Breadboard trials with the TI OPA172 showed better stability, but of course this is not an all-else-equal comparison.
  • The input impedance, $R_{13}$ in the mixer, is set to a fairly large value of 10 kΩ. This means the computer or phone is seeing a load that looks more like a “line in” than a set of headphones. In my experience this can cause noise in the input source to have a very apparent audio character. In other words, the system sounds crummy because the noise from the source is apparent. I suspect either of the alternate designs (depicted below) would help, but I have not tried them. The symptom is often evident with very sensitive headphones (Etymotic ER-4S) and can be treated with an in-line attenuator. I am not clear on whether the power delivered by the phone is lost (sunk to the virtual ground at the negative input of the op amp) or delivered to the load. If it is delivered to the headphones, than the low impedance 32 Ω version could additionally benefit power management. Indeed a non-inverting gain stage might make sense either in the variable gain preceding stage or in a post-mixer design. Presenting low impedance to the computer or phone may not help–some computers or phones work very well when presented with high impedance.
  • The gain of each stage in the imagined upgrade is better balanced. The initial pre-amp stage transimpedance amplifier is fixed and is only a little greater than unity so that its output is compatible with receiving phone or computer. The gain stage for the mic is variable, between 0 and about 5× voltage. The mixer stage has unity gain for the computer or phone source, but could easily be configured to have a factor of two or more gain for the mic with only unity gain on the supply from the computer or phone. At the needed gain values relatively little benefit may come from balancing the gains, but it seems like it would be a small improvement.
  • The design should be moved to a printed circuit board with surface mount components. The size would be reduced from about 2×3 inches to 1.5×2 inches (50% reduction in area) or smaller, see PCB layout figure at the end of this post.
  • This design has not been, in any way, optimized for total system power. I cannot even compare the ratio of quiescent power to dynamic power–and this seems somehow to suggest possible improvements.

 

Alternate input designs. On the left a unity-gain mixer presents a 32 Ω impedance to the computer or phone (on $V_2$). On the right, a voltage divider presents about 32 Ω to the source but leaves the amplifier as a 10 kΩ input amp–simpler modification of the circuit.
Example PCB layout with a SIPP quad op amp chip and 0805 series surface mount resistors. Some capacitors are electrolytic or film, and thus through-hole designs.

Hexagonal Blanket Dimensions

hex_geometry

Look at the right-most figure in diagram. The small triangle defines the all the major dimensions of the hexagon. Assuming the user measures the edge-to-edge dimension $c$, he or she can calculate the rest of the measurements. A simple right-triangle expression gives the relationship between $s/2$ and $c/2$, and is readily solved for $s$ in terms of $c$,
$$ \frac{s}{2} = \frac{c}{2}\tan\left(30°\right) $$
$$  s = c\tan\left(30°\right) = c\frac{\sqrt{3}}{3}. $$

Similarly, the Pythagorean formula gives the relationship between $c$ and the two other dimensions,
$$  d = \sqrt{ c^2 + s^2} = \frac{2c}{\sqrt{3}}.$$

Simplifying this equation by substituting for $s$ into the previous equation and simplifying produces
$$  \text{long pitch} = s + \frac{d-s}{2} = \frac{s+d}{2}  = \frac{\sqrt{3}}{2}c \approx 0.87c. $$

A blanket $n$ hexagons by $m$ hexagons will be approximately
$$
0.87c\,n \times m\,c, $$
where the $m$ and $n$ dimensions are as shown in the next figure.

hex_packing

If a blanket will be wider at the ends, as shown in the figure, then $n$ will be odd. The total number of hexagons will then be
$$ \text{number of hexagons} = m \frac{n+1}{2} + (m-1)\frac{n-1}{2}. $$

In the example there are $(n+1)/2=5$ tall columns and $(n-1)/2=4$ short columns. So there are 6×5=30 hexagons in tall columns and (6-1)×4=20 hexagons in the short columns, or 50 hexagons overall. Using equation for blanket size and assuming $c=10$ inches, the approximate dimensions of the finished blanket are 9×10×0.87 by 6×10, or 78.3 by 60 inches.

Launch-o-Rocket

School, from our house as the crow flies, is 5.73 km. If we neglect air resistance and deal strictly with ballistic flight then we can materialize a wonderful fantasy. Starting in the backyard, extending over the top of the house, is a launch-o-rocket, a rail-like launcher that accelerates the school-bound student until he or she can cruise over the city and arrive without bother of traffic. Our charter is to find the acceleration of the student from the launch-o-rocket.

launch-o-rocket

Finding the Initial Velocity

We rely on the well-known fact that the maximum distance in a throw occurs when the departure angle is 45°. The vertical speed and the horizontal speed are equal. We denote these two identical speeds as $s$. Since distance is time multiplied by speed, the distance from home to school $d$ is
$$  d = t\cdot s.$$

We know the distance $d = $ 5.73 km.

Turning to the vertical speed, the student departs the launch-o-rocket with vertical speed $s$, but is immediately subject to gravitational acceleration. Since the student’s upward flight is exactly matched by his or her downward flight. Because the flight is matched, the student spends $t/2$ time rising and $t/2$ time descending. Since the student has no vertical speed at the top, we know that his or her speed is
$$  s = g\frac{t}{2},$$

where $g$ is the gravitational acceleration 9.8 m/s2.

Now, we have a system of equations

$$  d = t\cdot s $$
$$  s = g\frac{t}{2}.$$
The system looks like it has a many variables, but really there are only two, $s$ and $t$. We know $g$ and $d$. To solve the system we substitute for $s$ in the first equation with the second to get

$$  d = tg\frac{t}{2} = g\frac{t^2}{2}$$
Solve for $t$
$$   t = \sqrt{\frac{2d}{g}}
= \sqrt{\frac{2\cdot 5.73\,\text{m}}{9.8\,\text{m/s}^2}}
\approx 34.2\,\text{s}.
$$
Not a bad commute, a little over half a minute.

With $t$ in hand, we can find the magnitude of the initial velocity. Remember that the initial velocity is $s$ in the horizontal direction and $s$ in the vertical direction, so the speed when leaving the launcher is
$$
\left| \mathbf{v}_0\right| = \sqrt{s^2 + s^2} = \sqrt{2s^2} = s\sqrt{2}.
$$
The initial speed the student must attain is given by the very first equation, $d = s\cdot t$. Solving for $s$ with the value of $t$ we found, we get

$$  s = \frac{5.73\,\text{km}}{34.2\,\text{s}} = 168\,\text{m/s}. $$

Finding the Acceleration

The ramp lives on a footprint that is about 80 ft, or 24.4 m. It is also 24.4 m tall, so special zoning is surely required! The rail of the launch-o-rocket is the hypotenuse of a triangle, and that triangle has sides 24.4 m, and a total length of $\sqrt{2}\cdot 24.4\,\text{m} = 34.5\,\text{m}$.

The formula for position after a period of acceleration is
$$   p = \frac{1}{2}a\tau^2.$$
For our system, we also know that the acceleration is the change in speed divided by the change in time. Our speed goes from zero to 168 m/s in $\tau$. Again, we have a system of equations,

$$  34.5\, \text{m} = \frac{1}{2}a\tau^2 $$
$$  a = \frac{168\,\text{m/s}}{\tau}.$$

Solve for $a$ by first solving the second equation for $\tau$, and then substituting that result into the first equation to get

$$   34.5\, \text{m} = \frac{1}{2}a\left(\frac{168\,\text{m/s}}{a}\right)^2 $$

$$   a = \frac{\left( 168\, \text{m/s}\right)^2}{2 \cdot 34.5\,\text{m}}
= 407\, \text{m/s}^2 = 41.5\, g. $$

The typical onset of death occurs when acceleration exceeds about $10g$, so unfortunately, the launch-o-rocket is a single try system.

300 Million Years Ago

This weekend my family came with me to hunt fossils in the Jemez mountains of New Mexico. We hunted fossils along Route 4, where I understand collecting is legal and ethical. The fossils we were looking for are quite common, mainly brachiopods (similar to clams), and crinoids (a kind of anemone). These fossils are common in the Pennsylvanian group, especially in the Madera subgroup. These strata were laid down in the Late Carboniferous period from about 323 to 299 million years ago.  

I had excellent fun assembling our fossil hunting map. I used the grand open source QGIS geographic information system software, importing the road layers from the Open Street Map project through QGIS’ built-in plug in. The topographic information came from the USGS 1 m digital elevation model, which I traced at 25 meter intervals. The New Mexico Geological Survey provided a very detailed geological map of the Jemez Springs area, from which I selected the Pennsylvanian Madera sections. The total map is assembled in the following graphic. 

GeoMapSm

My daughter found a crinoid calyx, or at least I believe that is what it is.20170730-145520-02

You can see the fan-like structure at the top of the crinoid tapering to one end where the frond-like structures joined the stem.

20170730-125033-225

My son found a brachiopod, which was nearly completely isolated from the surrounding matrix, and it is nearly flawless without preparation.20170730-145621-04

I composited three perspectives of the same fossil to show all angles.

Brachiopod

I found a collection of small sesame-seed sized bumps, which I believe are fusilinids. These are shells deposited by single-cell animals, which makes them gigantic as single-cell animals go. I’d like to cross-section one, since some fusilinids have really complex structures.

20170730-130124-249

We also found an assortment of random bits piled together. It seems like a story of the past, I just can’t read. I don’t know what all the elements are, but I recognize sundry crinoid stem segments and shell pieces. I don’t know what the long stem-like structure is left of center, but it has a fascinating look.

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We had fun, found far more fossils than I expected, of far more types. Next, I want to learn some amateur fossil preparation. So amazing to hold the remains of something that lived 300 million years ago in your hand.

Hot Soup!

My kids blow on soup to cool it down. Sometimes they blow like a tornado and most of the soup exits the spoon rather than entering the child. I always tell them to blow gently—it will cool just as fast.

Well, we put the theory to the test. For cleanliness, we simulated a broth soup with hot water. Viscous soups, like cream soups, might be different.

20170114-100901-02

For apparatus we mounted a spoon in a third hand tool. A thermistor temperature sensor was affixed to have the sensor at the lowest point in the spoon’s bowl. We had a small hand-held anemometer to measure the air speed at the spoon. We transferred hot—nearly boiling—water into the spoon with the turkey baster. The data logger, my own design, recorded the temperature.

20170114-100921-04_sm

Each of three test subjects blew on the soup to cool it. Each person blew lightly or strongly. We attempted to calibrate the airspeed at the spoon during an exhale. The picture below shows the first test subject (Dear Daughter) measuring the air speed. The anemometer is aligned with the spoon. Each subject attempts to hold their head in the same position.

 

20170114-101647-06_sm

Each subject blew on the spoon until the thermistor reading fell below 30°C. We recorded the start time and the stop time as indicated by the data logger. The start and stop time became cut points in the data processing.

20170114-104736-19_sm

We did all the experiments over about an hour, and left the data logger running the whole time. The plot of temperature is shown next. The spikes correspond to times when we recharged the spoon with hot water. The drops at the bottom of each trough correspond to our evacuation of the remaining water from the spoon.

plot_total_datalog

A cut portion of the timeline, corresponding to each experiment, is fitted to an exponential function of the form Temp = A×exp(time×B). The time constant for these fits is –1/B. The time constant corresponds to the amount of time for the temperature to drop 73% of the way to the ambient temperature.

plot_single_curve

The time constants from each trial also describe a curve as a function of the air speed. I fitted these data with another exponential function, and although the fit is not exact, it is satisfying close to the data.

plot_tc_v_airspeed

Each point color in the graph represents one person’s attempt. The dark blue point in the upper left is the a control where nobody blew on the spoon. The red point in the lower right corner corresponds to my son’s fastest effort, which removed about half the soup from the spoon.

To summarize the results, faster air speed does cool the soup considerably faster—meaning that I was not correct. My recommendation, based on the data, is to blow as fast as possible provided the soup is not sloshing out. You are welcome to use this data next time you’re trying to convince a young child to cool their soup properly. Your mileage may vary.

Rocket Stove

Maybe you’ve stored 100 pounds of wheat kernels, 75 pounds of beans, barrels of water and you’re all set for whatever municipal unreliability may bring. One question:

How will you cook the food you’ve stored?

In Food Storage and Refried Beans, back in April 2009,  I determined that to cook 100 pounds of beans would take about 4.7 gallons of white gas (Coleman fuel). Assuming the rest of a typical day takes a little less gas, you would still have to store about 10 gallons of gas to service that much food. While this is doable, it is certainly a hazardous amount of fuel. My personal solution is my own take on the Rocket Stove.

20160807-080546-108

We have a wood burning fireplace, but it is not set up for cooking. However, we keep wood around for the cold winter nights. Obviously, mankind has cooked on wood basically forever. So, obviously it is possible. I was introduced to the rocket stove developed by Aprovecho, which is intended to reduce fuel consumption by more efficiently transferring the wood’s energy into the cookpot, reduce air smoke and soot inhalation by combusting more efficiently, and improve burn safety. They have ten design principals, summarized:

  1. Insulate around the firebox. I do this by using insulating kiln brick (about 0.65 g/cm3).
  2. Place an insulating short chimney directly above the fire. Mine is about 9 inches high, made by two races of insulating brick.
  3. Heat and burn (just) the tips of the sticks. The shortness of the firebox accomplishes.
  4. Heat is regulated by the amount of fuel. I have no damper, which their research shows is not effective.
  5. Maintain a good fast draft through the fire. This is accomplished both with the chimney and a recovered steel grate that creates an air channel under the burning fuel.
  6. Too little draft makes excess smoke. See principle 7.
  7. The opening, size of spaces, and chimney should all be about the same size. Specifically they recommend a 12 cm square opening (4.75 in), which is about 3.5 inches, and is probably slightly too small.
  8. Use a grate under the fire. See principle 5.
  9. Insulate the heat flow path. My entire structure is made of insulating kiln brick.
  10. Maximize heat transfer to the pot with properly sized gaps. I have not yet begun this phase of development.

For an initial design I used twelve insulating kiln bricks. Four make a floor—insulated enough, I think, to be used on a wooden stand. Two were cut into plugs to make the sides complete, and the remainder were stacked to make a square chimney and burn chamber. The burn chamber as seen through the chimney is filled with embers.

20160807-081438-123

I scrounged and bent a wire rack to make a grate that retains a channel for air flow under the combustibles.

20160807-080551-110

On top I used four small stones to make a burner. This is very much the wrong design for quickly heating water, but it worked for a test run.

20160807-080556-113

Actually, it worked for three test runs. Yesterday we boiled water for tea.

20160806-090858-90

This morning the kids helped make oatmeal on it. This evening I caramelized onions on it while grilling burgers.

My impression is that this device is the bee’s knees! The smoke was minimal (not as minimal as I would have liked, but largely avoidable). The amount of wood burned was about 4 linear feet of thumb-diameter sticks. The stove is stable, even with my crummy burner. I think it would make a nice patio fireplace for autumn evenings. Small, but controlling the smoke makes it much more pleasant to be around.

I do look forward to improving it. It is a pain to move, since it is about 45 pounds and doesn’t hold itself together. It is too low to cook on comfortably. Its heat transfer are near the pot is not well sized. This all requires work. I would also like to measure the efficiency of the stove. Always more fun to have!

Masterbuilt Smoker Upgrade–Ribs Hanger

I love ribs, and I love the way they come out of my Masterbuilt electric smoker. Actually, it’s my dad’s smoker but I keep it safely at my house. The problem with ribs is the time. The late-night clean up, after cleaning and rubbing the ribs the night before and cooking six hours, is almost too much. The worst thing to clean is the racks. The chromed welded-mesh racks (picture below) sit in the smoker like oven racks. The racks’ many textures make them difficult to clean. My best success is to spray them with cooking spray before using, then soak them in the sink for an hour or two, followed by a brushing, and then often steel wool. They don’t get clean enough in the dishwasher.

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This post is about making ribs without the cleanup headache.

My friend Scott owns the same kind of smoker, and provided the first piece of wise council. Instead of lining the water pan and drip pan with foil, put a disposable pan aluminum pan in place of the water pan. I also hang aluminum foil skirts on the sides of the smoker to keep from having to clean the sides as shown below. I use a 10.5×13 inch disposable pan purchased at Costco. I deform the pans a little to fit better.

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To dispense with cleaning the racks demands an alternative. I built a hanger to suspend the ribs from near the ceiling. Then, I bent cheap stainless skewers into a shape that holds the ribs along their length. One skewer is native, unbent. The other has the end bent up and then into a loop. Then the two skewers interlock. String tied at the top holds the ribs in.

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Each pair of skewers holds a half rack of ribs, squeezed. My design keeps the ribs upright with minimal risk of falling.

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I align the loops at the top of the skewers so that they are both held.

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I built a hanger out of piece of brass angle iron. I drilled and tapped along the length, and ran 2-inch 8-32 screws through, leaving plenty of length to hang the holders from. The rack fits snuggly inside the smoker, in fact too snuggly. However, the idea of the design seems sound. The angle iron rests on the wire slides Masterbuilt included. I use a steel clip. If I redo this, I’ll probably use a threaded hole on the inside of the wire slide, and a fender washer to hold the angle iron on.

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To load the smoker, I hang the ribs from the screws.

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To sauce the ribs, I use tongs to pull a whole rack out. The large rings in the skewer make them easy to take off for a saucing.

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The skewers’ simple geometry makes them a breeze to clean. They came off the ribs without damaging the crust we work so hard to get. In addition to the easy clean-up, the method causes the fat to drip off the ribs and into a pan, rather than onto the rack of ribs below. The angle-iron hanger rack also works to hang chicken halves with a steel s-hook or a string, also with easy clean-up.

Useful Range of Vivitar Wireless Remote Release

Vivitar brands a radio-frequency wireless remote that is available on a budget. The version shown below is configured for a Nikon D300; the pigtail can be changed for other camera designs. The remote has a telescoping antenna that extends to about six inches. The radio receiver is about 1.5 by 2 inches as seen from the top, and stands off the table about 3/4 inch. The receiver has a plastic foot that fits in the camera’s hot shoe.

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For an upcoming shoot of a dance performance my two-person team is planning to work one camera dynamically up close, working on solo dancer shots and facial expressions. A second photographer will be in the mezzanine working context and group figures, as well as providing a higher angle. In our last shoot I worked close to the stage, mainly on single-dancer shots. Usually a single-person subject looks best when her background is simple and clear. During group figures I could find no position near the stage that produced satisfying composition. In other words, during large group shots I had the choice of scrambling to a different perspective or sitting idle. I want a different choice.

The new choice is to put a third camera either on the mezzanine left, or better on the balcony. With a wireless remote I can easily capture a full context shot. I can set the balcony cam with a fixed focal length lens, fixed aperture, and fixed focus point to get a consistent context shot. When the stage situation demands context shots, I’ll drop back and work the remote. Assuming the remote works.

Two main issues could get in the way of the remote. The first is batteries. Both the remote and the receiver use a battery. Should be easily solved with new batteries prior to the shoot. The second one is distance; the remote must have enough range. I used a simple test to gauge the remote distance. My son stood by the camera on the sidewalk, and I walked a few steps at a time up the sidewalk. He would give me a thumbs up if the camera shutter released, and I could take another few steps further. I marked the final distance with chalk. We performed the test with the remote’s antenna collapsed, and with it extended. An outdoor test means the RF has little chance to scatter off walls and ceilings. I expect the remote’s indoor range will exceed its outdoor range.

Antenna Collapsed: 53 feet max range
Antenna Extended: 148 feet max range

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Thistle and The Bear on Autumn and Halloween

Thistle and the Bear talk about autumn, and especially about Halloween traditions.

 

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My seven year old daughter practices her typing with a writing prompt most days. When asked to type about what she likes about Halloween, the wrote this:

I like Halloween because we have a funny dinner and we go trick-or-treating in the dark. That’s fun to do because we are out of the house at night and ringing people’s doorbells and collecting candy in our bags that hold candy lasting til Christmas. We are usually out trick-or-treating for a long time in the night. I like being a mouse.