Week 12

What is water marbling?

Water marbling is a surface decoration technique that dates back centuries — originating in Central Asia and later refined in Turkey (where it is known as ebru) and Persia. The technique involves floating paint on the surface of water and manipulating it into patterns before transferring the design onto paper, fabric, or other materials.

The paint floats because it is mixed with a surfactant or applied onto a size — typically a viscous solution of carrageenan or ox gall — that prevents the pigment from sinking. Once the pattern is formed by dragging combs, styluses, or other tools through the floating paint, a sheet of paper is laid on the surface and lifted, picking up the design in a single transfer.

Our team's machine automates this process: a CNC-controlled dropper system deposits precise amounts of paint onto the water surface at programmable positions, allowing repeatable and parametric marbling patterns that would be very difficult to achieve by hand.

Group Assignment

The full group documentation — including the machine's electronic design, firmware, motion system, and final results — is available on the group page.

Overview

My individual contribution to the machine covered six areas: researching and sourcing the paints and materials needed for the marbling process, cutting and preparing the metal structure, painting and finishing the profiles, testing servo angles for the dropper mechanism, testing paint height and color combinations, and producing the group presentation slide.

00. Paint Research & Material Sourcing

Before any physical work began, I researched what types of paint are compatible with the water marbling technique. Not all paints float — the paint needs the right density and surface tension properties to spread on water without sinking or clumping.

I ran initial tests at home with two types of paint I already had: textile paint and acrylic paint. Textile paints are water-based and tend to have a thinner consistency, while acrylics are denser and require more dilution to float correctly. Testing both allowed the team to understand the behavior of each before committing to one for the final machine demonstration.

01. Materials — Metal Structure

For the structural frame, we needed specific lengths of a ¾" metal profile. I was responsible for measuring, marking, and cutting all the pieces to size.

• 1 Measured each piece to 35 cm and marked the cut line using a metal scriber and a square.
• 2 Cut the profiles on the metal cutter saw wearing full protective gear: overall, face shield, soldering gloves, and safety footwear.
• 3 Repeated the measuring and cutting process for all required pieces.
• 4 Deburred all cut edges with a file to remove sharp burrs.

Measuring & marking

Each piece measured to 35 cm and traced with a metal scriber and square to ensure a clean, accurate cut line.

Cutting on the metal saw

The profiles were cut on a metal cutter saw. Full PPE was required: face shield, overall, soldering gloves, and safety footwear.

Filing the edges

After cutting, a file was used to remove all sharp burrs from the cut edges before assembly.

02. Painting & Surface Finish

Once all pieces were cut and deburred, I prepared and painted the metal profiles so the final machine would have a clean, finished appearance.

• 1 Sanded all profiles to remove surface imperfections and smooth the metal.
• 2 Wiped off the sanding dust with a damp cloth and let the pieces dry completely.
• 3 Applied 2 coats of primer to fill micro-imperfections and improve paint adhesion.
• 4 After the primer dried, applied 2 coats of silver spray paint for the final finish.

Sanding

All profiles sanded to remove imperfections and create a surface that holds primer and paint properly.

Primer coat

Two coats of primer applied to fill micro-imperfections and help the paint adhere evenly to the metal surface.

Silver paint

Two coats of silver paint applied over the dried primer for the final clean finish.

03. Checking Servo Angles

The dropper mechanism uses a servo motor to press a dropper and release a small, controlled amount of paint onto the water surface. I was responsible for finding the correct angle range at which the servo arm activates the dropper effectively.

After connecting the servo to the ESP32 and the external power supply, I used the following code in Arduino IDE to sweep through angles and identify at which point the arm correctly pressed the dropper to release a small, consistent drop of paint.

#include 

Servo myservo; 
int pos = 0;    // Variable para almacenar el ángulo deseado

void setup() {
  Serial.begin(115200);      // Inicializamos la comunicación serie
  myservo.attach(25);        // El servo sigue en el pin 25
  
  Serial.println("Introduce un ángulo entre 0 y 180:");
}

void loop() {
  // Comprobamos si hay datos disponibles en el Monitor Serie
  if (Serial.available() > 0) {
    // Leemos el número entero que escribas
    int anguloManual = Serial.parseInt();

    // Validamos que el ángulo esté en el rango permitido
    if (anguloManual >= 0 && anguloManual <= 180) {
      pos = anguloManual;
      
      Serial.print("Moviendo servo a: ");
      Serial.print(pos);
      Serial.println(" grados.");

      myservo.write(pos);    // Movemos el servo a la posición única
    } else {
      Serial.println("Por favor, ingresa un valor entre 0 y 180.");
    }
    
    // Limpiamos el buffer para evitar lecturas erróneas
    while(Serial.available() > 0) Serial.read();
  }
}
              

Servo + ESP32 setup

The servo connected to the ESP32 and powered through the GW Instek GPE-3323 bench power supply.

Arm adjustment

The original servo arm was too short to reach the dropper effectively. Kamil updated the design parameters to account for this.

04. Color & Height Testing

In this phase I worked together with Carlos to validate two critical variables: the height of the dropper above the water surface, and which color combinations produced the best visual results.

The height matters because dropping from too high causes the paint to break the water's surface tension and sink rather than float. Dropping from too low limits the spread of the pigment. We tested multiple heights to find the optimal range.

Height testing

Testing different dropper heights to find the range where paint floats correctly without breaking the surface tension of the water.

Color combinations

We tested multiple color pairings and identified 4 combinations that produced clear, well-defined marbling patterns on the water surface.

05. Render

As part of the documentation process, I created a render of the water marbling machine to visualize the final assembly before it was fully built. This helped the team review proportions, structure, and the placement of components.

05. Group Presentation Slide

Finally, I was in charge of designing the group slide summarizing the machine, its purpose, and the team's process. The slide was used for the weekly review presentation.