MATERIAL¶

BIO PLASTIC PROCESS¶

Materials¶

Algae (source material for alginate extraction)
Sodium alginate powder
Water
Glycerine (plasticizer)

Tools & Equipment¶

Hand blender (immersion blender)
Measuring cup (ml scale)
Precision scale (grams)
Test tubes or small containers (for dried alginate slabs)
Molds or casting surfaces (for casts)
Spatula or spoon (for handling the mixture)
Fan (for air circulation & faster, more even drying)
Refrigerator (overnight resting)
Microwave (short heating before casting)
Ultra-low temperature freezer (−80 °C)
Containers for freezing & storage

Step-by-Step Procedure for Alginate Extraction from Algae¶

Step	Procedure	Description / Purpose
1	Washing the algae	Removal of dirt, salts, & other impurities
2	Freezing the algae	The algae are stored for 48 hours at −80 °C in an ultra-low temperature freezer
3	Alginate separation	Due to the extreme cold, alginate separates from the algal structure
4	Material fractionation	Light green / whitish material: isolated alginate Dark green material: remaining algal biomass (de-alginated algal residual material)
5	Drying the alginate	The isolated alginate is dried
6	Formation of alginate slabs	After drying, the alginate forms solid “slabs”, which are stored in test tubes

Alginate–Glycerine Bioplastic Recipe¶

Bioplastic: Alginate Drying Process¶

The drying time of alginate bioplastic strongly depends on the shape, thickness, & environmental conditions.

Typical drying times¶

Thin layers / films (1–2 mm): 12–24 hours
Thick casts / molds (≥ 5 mm): 2–5 days, sometimes longer

Factors affecting drying time¶

Air humidity: high humidity → slower drying
Temperature: warmer conditions (20–25 °C) → faster drying
Air circulation: good airflow accelerates drying
Glycerine content: more glycerine = longer drying time & higher flexibility
Thickness: the most important factor

Tips for even drying¶

Dry on smooth, non-absorbent surfaces (silicone, glass, PE foil)
Avoid direct sunlight (may cause warping or cracking)
Carefully turn pieces after ~24 hours if needed
For workshops: use several thin layers instead of one thick cast

Step	Ingredient / Action	Amount	Notes
1	Water	100 ml	Base liquid
2	Sodium alginate	3 g	Adjust depending on desired thickness & stiffness
3	Substrate (wet)	0 - 25% g	Adds texture and structural variation
4	Glycerine	5 g	Plasticizer for flexibility
5	Mixing	—	Mix thoroughly using magnetic stirrers until homogeneous
6	Casting	—	Pour into frames or molds
7	Drying	—	Air-dry until fully dry (1–5 days depending on thickness)

other option: - Leave the mixture overnight in the fridge to fully hydrate the alginate & remove air bubbles - Pre-heating Heat the mixture in the microwave for 10 seconds - then casting

For my first material experiments, I used a recipe that I received from Anastasia Pistofidou. I started from the basic recipe & developed several experimental series based on it.

I worked with both commercial sodium alginate & self-extracted alginate, which was produced by Maria’s students: Nina Isabella & Lagunes Jovel from a mixture of different seaweed species.

The seaweed was collected in spring 2025 on the beach of Bela Cruz.

As a substrate, I used the remaining seaweed biomass, meaning the material left after the alginate extraction process (de-alginated biomass).

Test Series 1 – Substrate particle size¶

I tested different preparation methods:

Used directly
Blended
Sieved
Blended & sieved

Test Series	Preparation Method	Description of Treatment
1	Used directly	Substrate used without further processing
1	Blended	Substrate mechanically blended
1	Sieved	Substrate sieved to obtain uniform particles
1	Blended & Sieved	Substrate blended and then sieved

Test Series 2 – Glycerin content¶

(in combination with self-extracted alginate) Variation of glycerin from 0–15%, 20 g per Petri dish (Ø 9 cm).

Glycerin %	Glycerin (g)	Alginat (g)	Wasser (g)	Total (g)
0 %	0.00	0.60	19.40	20.0
5 %	1.00	0.55	18.45	20.0
10 %	2.00	0.52	17.48	20.0
15 %	3.00	0.50	16.50	20.0

Test Series 3 – Biomass content¶

(in combination with sodium alginate) Variation of biomass from 0–25%, 20 g per Petri dish (Ø 9 cm).

Biomass (%)	Biomass (g)	Sodium alginate (g)	Water (g)	Total (g)
0	0.00	0.58	19.42	20.00
5	1.00	0.55	18.45	20.00
10	2.00	0.52	17.48	20.00
15	3.00	0.50	16.50	20.00
20	4.00	0.47	15.53	20.00
25	5.00	0.44	14.56	20.00

After drying & evaluation, I selected the following parameters: - Substrate: blended biomass - Glycerin content: 5% - Biomass content: 20%

Component	Mass (g)
Biomass (blended)	4.00
Glycerin	1.00
Sodium alginate	0.44
Water	14.56
Total	20.00

Test Series 4 – Material Thickness¶

I then conducted a 4. test series to determine material thickness, testing 20–45 g per Petri dish (Ø 9 cm).

Test Series	Wet Mass per Petri Dish (g)	Approx. Wet Thickness (mm)	Approx. Dry Thickness (mm)	Observations	Evaluation
4	20 g	~3 mm	~1.0 mm
4	25 g	~3.5 mm	~1.2 mm
4	30 g	~4.3 mm	~1.5 mm
4	35 g	~5.0 mm	~1.7 mm	Selected	Optimal balance
4	40 g	~5.7 mm	~2.0 mm
4	45 g	~6.4 mm	~2.3 mm

I selected a final material thickness of approx. 1.7 mm, achieved with 35 g wet weight (approx. 5 mm when wet).

Component	Amount (g)
Water	180.0
Sodium alginate	6.5
Glycerin	12.5
Biomass (blended)	50.0
-----------------	----------
Total	250.0

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MID TERM PRESENTATION¶

PDF¶

NEW ALGINATE-BASED BIOPLASTIC RECIPE¶

Since fresh seagrass is now available, the bioplastic recipe needs to be adjusted accordingly.

Fresh Sargassum differs significantly from dried or previously desalinated material, both in composition & behavior. This requires a recalibration of the recipe & process, based on the following considerations:

Fresh seaweed already contains naturally occurring alginate → the added alginate content in the recipe must be reduced
Fresh seaweed contains a high amount of water → the water content in the recipe must also be reduced
Fresh seaweed is saturated with salt → desalination is necessary to avoid brittleness & instability in the final material

The following sections outline the material logic & scientific principles behind these adjustments.

WITH FRESH SEAGRASS / SARGASSUM¶

1. SALT CONTENT & DESALINATION¶

Osmolarity as a Material Process¶

Before addressing alginate content and recipe ratios, the salt content of fresh Sargassum must be reduced. This is achieved through osmotic desalination.

OSMOLARITY¶

Osmolarity describes the concentration of dissolved particles (such as salt ions) in a liquid. When materials with different osmolarities are in contact, water moves to balance these concentrations. Through osmolarity, salts contained in the seaweed diffuse into the surrounding fresh water until concentration equilibrium is reached. Desalination introduces osmotic stress that can weaken cell membranes, but the alginate-rich cell walls remain largely intact. Therefore, desalination represents a transformation of material state, rather than a loss of material substance.

Osmolarity & Seaweed Desalination¶

Step	Explanation
Osmolarity	Concentration of dissolved particles (salt) in water
Initial state	Seaweed = high osmolarity / Fresh water = low osmolarity
Osmosis	Water moves from low → high osmolarity
Process	Salt diffuses out of the seaweed into the surrounding water
Result	Seaweed becomes desalinated
Water change	Keeps external osmolarity low, allowing continued salt removal

2. SALTWATER VS. FRESHWATER STATE¶

Fresh vs. Desalinated Sargassum¶

Whether Sargassum is used fresh from the shore—still saturated with saltwater—or after being soaked in freshwater makes a significant difference, both materially and conceptually. The salt content directly affects the behavior, stability, and reproducibility of the material.

Fresh Sargassum (saltwater-saturated)¶

Contains high amounts of salt → affects drying behavior, crystallization, and material structure
Salt can:
Create brittle surfaces
Act hygroscopically (attract moisture)
Interfere with bioplastic recipes (binders behave differently)
Often stronger odor and faster biological degradation

Desalinated Sargassum (freshwater-soaked)¶

More stable and reproducible material properties
Binders (agar, alginate, glycerin) behave more predictably
Fewer salt residues & less uncontrolled crystallization
Easier to compare, document, and systematize (important for Fabricademy)

3. ALGINATE CONTENT IN FRESH SARGASSUM¶

Implications for Recipe Adjustment¶

In addition to salt and water content, fresh Sargassum already contains a significant amount of naturally occurring alginate. This directly affects the formulation of alginate-based bioplastics.

Estimated Alginate Content (Literature-Based)¶

Brown seaweeds like Sargassum typically contain 15–30 % alginate by dry weight
Some studies report alginate yields around 18–28 % of dry biomass
Pelagic Sargassum has been reported at ~7–10 % alginate (dry weight) in some technical studies

Important caveat:¶

These values refer to dry weight, not fresh (wet) weight. Since seaweed consists largely of water (often 70–90 %+), the alginate content relative to fresh weight is much lower.

Approximation for 100 g Fresh Sargassum¶

Dry matter: ~10–30 g per 100 g fresh seaweed
Alginate fraction: ~15–30 % of dry matter → Alginate ≈ 1.5–9 g per 100 g fresh Sargassum (approximate range)

Important to Know¶

The exact alginate content varies significantly depending on: - Sargassum species - Growth location & season - Maturity stage & environmental conditions The value given is therefore a realistic estimate, not a fixed number.

4. MATERIAL LOGIC — ALGINATE CONTENT¶

Fresh → Dry → Alginate¶

FRESH SARGASSUM (100 g)¶

≈ 70–90 % water ≈ 10–30 % dry matter Salt-filled cellular structure

⬇ drying / dehydration

DRY SARGASSUM (10–30 g)¶

Concentrated biopolymers Structural polysaccharides become dominant

⬇ alginate fraction

ALGINATE (≈ 15–30 % of dry weight) ≈ 1.5–9 g alginate per 100 g fresh Sargassum Structural binder within the cell walls

THE COLOR CHANGE OF FRESH SARGASSUM¶

From green / olive to brown¶

During the transition from freshly collected Sargassum to a processable material state, a noticeable color change occurred. While the fresh seaweed initially showed a green to olive tone, it gradually turned brown during desalination and preparation.

Why the color turns brown¶

This change is mainly caused by:

Oxidation¶

Exposure to oxygen during soaking, cutting, or drying leads to pigment degradation.

Pigment loss during desalination¶

Prolonged soaking in freshwater can leach out water-soluble pigments.

Heat exposure¶

Warm water or heating during bioplastic preparation accelerates chlorophyll breakdown.

pH changes¶

Acidic conditions convert chlorophyll into pheophytin, resulting in brownish-olive tones.

This color shift is a natural & expected transformation when working with fresh seaweed.

There are several possible approaches to dealing with color changes in fresh Sargassum, depending on whether the focus is on material control or conceptual expression.

1. Use antioxidants only as a preventive test¶

Antioxidants such as ascorbic acid can slow oxidation if applied early, but they cannot restore the original green color. They function as a preventive experiment rather than a corrective solution.

2. Prioritize pH control & reduced oxygen exposure¶

Maintaining a neutral to slightly alkaline pH & minimizing oxygen exposure helps slow pigment degradation while preserving stable alginate & bioplastic behavior.

3. Add pigments separately¶

Instead of trying to preserve the natural color, pigments can be reintroduced intentionally, allowing color to become a designed layer rather than a fragile material property.

RECIPE ADJUSTMENT¶

After evaluating the further material tests, this formulation was chosen based on insights gained from the material’s behavior.

Since fresh, desalinated Sargassum now replaces a drier substrate, the recipe needs to be adjusted to account for: - Water already contained in the fresh seaweed - Naturally occurring alginate within the Sargassum biomass

Original Working Recipe¶

#	Component	Amount	Function
1	Water	100 ml	Base liquid
2	Sodium alginate	(5%) / 5 g	Primary binder
3	Glycerine	2.5 g	Plasticizer for flexibility
4	Substrate (wet)	(20%) / 21.5 g	Texture & structural variation

Adjusted Recipe¶

NEW ALGINATE-BASED BIOPLASTIC RECIPE¶

with desalinated fresh Sargassum¶

#	Component	Amount	Adjustment Rationale
1	Water	60–70 ml	Reduced to compensate for water already contained in fresh seaweed
2	Sodium alginate	2–3 g	Reduced due to naturally occurring alginate in Sargassum
3	Glycerine	2.5 g	Kept constant; adjust later only if brittleness occurs
4	Substrate (fresh, wet Sargassum)	21.5 g	Kept constant for texture continuity & comparability