Aluminum Paste is a mixture of solvent or water and aluminum pigments with particle shapes and sizes that have been manipulated through a milling process to create aesthetic properties.
What is Aluminum Paste?
Aluminum Paste is a slurry of pigments and liquid. Both chemical solvents and water can be used as a liquid when producing aluminum paste.
What is Aluminum Paste used for?
Aluminum paste is a packaged metallic pigment or dust. Aluminum pigments are used to create the metallic aesthetics found in a wide range of paints, coatings and inks. Manipulating the particle shape and size within the coating, ink or masterbatch (ink for Graphic Arts and masterbatch for plastics) creates different effects. It is not enough to simply add pigments to a paint or ink. The aluminum pigments are combined with a dispersant comprised of solvent or water to create a paste.
Often, the Paste is referred to a slurry or a pigment slurry.
Why not use dry pigments?
The reason dry pigments are not typically used is for safety and easy handling. Aluminum flake and dust are referred to as fines. These airborne fines can quickly spread heat when ignited. If exposed to electricity, phenomena known as arch flash will occur.
The very dust used intentionally to aid rocket boosters and pyro techniques, presents severe hazards as a machining and thermal spray byproduct. Additionally, manufactures of coatings, inks or masterbatched containing aluminum metallic pigments do not want to create this hazardous dust during their production.
What are pigments combined with to create an Aluminum Pigment Paste?
A variety of solvents can be used to create paste. While the solvent used will depend on the end use, mineral spirit is common. Even water can be used should the paste be needed for water based coatings.
Water based aluminum paste is also used in lightweight concrete. A water and alkaline solution, mixed with aluminum, will give off gasses that result in small air pockets within the concrete. The result is a lighter concrete known as “aerated concrete.”
Is water based Aluminum Pigment Paste safe?
Generally, Aluminum flake pigments can react with water. When the two are combined, they create hydrogen. Hydrogen is a flammable and dangerous gas if not properly handled.
ECKART is committed to the safe production, handling and shipment of Aluminum Pigment Paste.
What markets does ECKART service with solvent and water based aluminum paste pigment?
ECKART offers a wide variety of pastes. Furthermore, we service many markets with our Aluminum Paste Pigment products. These include:
In the automotive industry typically high class aluminum flakes with excellent optical performance are use; e.g. so-called Silver Dollar STAPA® METALLUX 2000 and METALLUX 3000 series.These provide on top of their superior metallic brilliance a deep flop effect, which enhances the car body design, thus supporting curves and edges of the car body.
In high solid applications, a common approach to meet environmental legislation, non-degrading flakes STAPA® NDF product line is a commonly used pigment.
New product lines with even higher brightness and hiding power further allow formulation of brilliant effects in high solid formulations.
Recent market trends towards fine, structure less mirror effects can be met with SILVERSHINE 400 series; which is produced in accordance to latest development in careful Silver Dollar milling technology. Vacuum metallized pigments (VMP) or PVD pigments (product line METALURE) allow formulating true mirror finishes and have successfully introduced into automotive OEM market.
Additionally, the automotive industry has very much converted from solvent-borne to water-borne technology. Here ECKART offers a variety of different product lines for the different paint chemistries. Whereas STAPA® HYDROMIC, as additive technology, is more designed to give good gassing stability at a reasonable cost implication; the silica encapsulated STAPA® IL HYDROLAN technology provides very robust in use aluminum flake paste with excellent gas stability.
Refinish industry, where long storage times in the refinish sales lines are very common, together with storage in sealed can, any gas formation is not acceptable. Here the encapsulated STAPA® IL HYDROLAN grades haven to be best choice.
Refinish industry is also a target market for the recently developed STAPA® IL HYDROLAN Plus encapsulated aluminum paste pigment. By a process modification, the protective silica layer could be made more compact and dense, thus providing even superior gas stability in these critical automotive applications.
Metallic effect pigments are used in the paints and coatings industry for both their optical effects as well as for their functionality. Effect pigments are always lamellar (flakes) and their particle diameter is larger than the one of color pigments. While the particle size of color pigments is in the wavelength range of visible light, the flake diameter of effect pigments is generally around 5 – 45 μm.
In many cases the properties of metallic effect pigments can be deduced directly from the production process. The gold bronze pigments are dry milled in ball mills (Hametag process), but for safety reasons aluminum pigments are produced almost exclusively in a wet milling process adding white spirit (Hall process).The raw material - atomized, spattered aluminum with a minimum
purity of 99.5% according to EN 576 – is milled respectively shaped to flake-like particles in ball mills, filled with grinding aids (lubricant).
The milling parameters and the lubricant are determined by the application for which the aluminum paste pigment is intended. The pigment slurry is screened, pressed on filter presses and adjusted in mixers to a
ratio of 65% solids and 35% solvent.
The final product can be tailor-made for its later application by the addition of particular solvents or additives to the filter cake.
Aluminum Printing Ink Production Video
In the printing industry, aluminum pastes are used depending on the respective printing process and chemistry.
For solvent-based printing applications in flexographic or gravure printing, solvents with a low boiling point such as ethyl acetate are preferably used in the aluminum paste in order to ensure optimum drying behavior even at high printing speeds.
Pastes with a very low mineral oil content or mineral oil-free pastes are used for food packaging where low-migration regulations must be observed. By comparison, screen printers prefer to use solvents with a high boiling point such as butyl glycol, methoxypropyl acetate or methoxypropanol to achieve a smooth, uniform and highly brilliant surface in the printing application. Known products are included in the ROTOVARIO series; for low-migration products we recommend the ROTOVARIO FPG series for silky smooth or matte metallic effects. Mirror-like metallic effects can be created with products from the PLATINVARIO or METALURE® AE series. Under the series names ROTOSTAR, PLATINSTAR or ULTRASTAR, ECKART also offers ready-mixed printing inks for printing ink manufacturers. Depending on the requirements for metallic gloss, these series are also available as low-migration variants.
For aqueous flexographic or gravure printing applications, additive-treated or encapsulated pigment pastes are used to ensure an optimum combination of water stability and brilliance. The water stability of products from the STAPA® HYDROXAL range is so high that these products can offered as a purely water-based dispersion. Similar products are included in the STAPA® HP Z range or the ROTOSTAR Aqua range of printing inks. Low-migration products round off ECKART's portfolio here as well.
Aluminum pastes for UV-drying flexo or offset printing applications are offered in UV-acrylic-based systems. The corresponding product series (METALURE® UV, ROTOVARIO UV) have been modified to improve durability and avoid gelation of the finished printing ink. This avoids the reaction of the metal ions with the UV binder leading to a polymerization reaction. During drying, the emitted light initiates only the reaction with the binder, while the pigments remain inert. The surface modification of the pigments facilitates their optimal alignment in the printing film for high brilliance.
For use and optimum ink transfer in offset printing, the size of the aluminum pigments must be much smaller than for other printing applications. Due to the oil-based character of the printing inks and for a good metallic printing result, the respective solvents in the metallic pigments pastes are precisely matched to the oil / mineral oil used in the formulation. Additionally, modified inks that meet the various regulatory requirements are also available (METALSTAR, UNIPAK, TOPSTAR) for the printing inks manufacturers.
As metallic printing inks are used in a wide variety of applications, ECKART printing inks comply with the highest regulatory standards. Our Safety and Regulatory Department provides regular updates on the latest listings and ingredient regulations to provide our customers with all the information necessary for product safety. In addition, aluminum pigments do not pose a problem for recycling processes. In this way, recycled substrates can be further processed into high quality, reusable products such as paper.
For plastics applications high boiling oils are used as liquid component. It has to be solvent- and water-free. It is also important that the oil does not migrate to the surface. Another criterion is, the pasting agent must have food approval. Many plastics applications are for the packaging industry. The products ECKART is offering to the plastics industry are easy to incorporate in polymer systems, have high metal content (80%) and are dust free.
You can learn more about this when you visit our booth at this year's K-Fair.
Metallic effects is a major influence in the cosmetic market, for solvent-borne nail polishes. Our product line SILVERDREAM embodies impressive metallic effects that offer captivating silver sparkle, mirror and prismatic appearances with vacuum metallized pigments made by our unique PVD technology.
What are some of the optical properties aluminum flake paste can provide?
There a number of characteristics that pigment slurries can provide, including:
- Color Shade
- Brilliance (Sparkle and Metallic gloss)
- Color Saturation
- Tinting strength (hiding power)
- DOI (Distinctness of Image)
How are these optical properties achieved?
As stated above, we achieve these visual effects through manipulation of aluminum flake paste pigments. This includes:
- Particle size distribution
- Particle Shape
- Smoothness of the surface
- Pigment orientation in relation to the surface
- Wetting behavior (leafing vs non-leafing)
Can ECKART help me find the product that is right for me?
Absolutely. We have a team of technical professionals that are here to help you find the best aluminum pigment for your needs. Please notice, we do not promote producing samples for everyone for free; it depends on the individual request. Please contact us!