alginate header

Alginate Impression Material

INTRODUCTION

Alginate impression material has remained the best material employed by dentists in making patients' teeth dental molds for many years. The main reason behind their choice of alginate impression material is its skin-safe nature and as a hypoallergenic substance, it is suitable for youngsters. This fantastic material is used in making limb impressions as well as other body parts for prosthetics.  As a result, sculptors and artists started to test the possibility of working with this mold-building compound for their works, and in the process of this experimentation, they found that they can produce molds of their model's poses, to aid in creating their pieces of sculpture even without a live model. 

Inanimate objects don't get tired, unlike posing models. As a result of this initial practice, artists initiated the art of life casting for the sake of the art pieces that could be created as a result. Dental alginate has a weakness though. It cures very quickly—within 2-3 minutes—thereby limiting its usage to minor body molds. There simply wasn’t enough time to make larger pieces before the material set. So, suppliers adjusted its formulation to accommodate creative demands, producing another material called prosthetic grade alginate. We will be showing you the strengths and weaknesses of prosthetic grade alginate in this article, and we will show how to use it to make flawless lifecasting molds.       

Giant Kelp at Birch Aquarium, San Diego CA

Figure 1. Boy observing giant kelp (Macrocystis pyrifera) at the Birch Aquarium, San Diego, CA. Kelp can grow 2 1/2 feet per day and when full grown can be as high as 130 feet. Kelp is harvested to extract its algin used in the production of skin-safe impression mold material.

The Historical Background

E.C. Stanford, a pharmacist from the United Kingdom, invented a compound called algin from alginic acid extracted from seaweed in 1883. He discovered from his research that the majority of brown seaweeds have this compound in the form of complex sodium salt, potassium, magnesium, and calcium. This reminds me to explain that in mixing this latest prosthetic grade impression material formulation, you do not need to increase the mineral salt quantities, because it will obstruct the impression material’s curative periods. These excessive salts are found in “hard water” when they are dissolved in water.           

The actual mixing of alginate differs with each kind of algal. Mass production of algin salts did not start until 1929, when a California—based company called Kelco Company (a company which is now a subsidiary of Merk) began producing this compound in large quantities. Since then, several companies in countries like USA, Canada, United Kingdom, Norway, China, and Japan have gone into the production of algin salts (click here). To find the total number of countries in which algin salts-producing companies are located, click here.        

The development of the compound used in making dental impression material for the dental industry has been credited to the United States Navy. The compound was developed as an alternative to another compound called ‘agar agar.’ Before World War II, Japan was the only country producing ‘agar agar.’ But as a result of the conflicts between these two countries, Japan cut off its supply of the compound. This forced the USA to look for an alternative.

Algin salts have become an essential pharmaceutical ingredient over the years. As a hydrocolloid that originates from vegetable as well as occurring as a vital component for marine brown algae, algin salts provide the plant with strength and plasticity. To extract algin (also called alginate) from its natural seaweed origin, over twenty stages are involved.

An Exceedingly Valuable Product

The algin industry is a huge one. It has been projected by Grand View Research, Inc. that by the year 2025, the algin market will have reached USD $923.8 million. This projection is based on the fact that the compound finds its way into several uses in the pharmaceutical sector as well as serving as a suspension stabilizer, disintegrate, thickening agent, and film-forming agent for tablets.       

More than 22,679,619 kilograms of alginic acid is being extracted annually across the globe today. The giant kelp, known as Macrocystis pyrifera is harvested from substantial beds off the shores of California, Mexico, the North Sea and Asia.    

harvesting kelp

Figure 2. Kelp harvesting in California waters. This is the first step in the production of alginate.

More than 120,000 tons of this compound are being realized on an annual basis using cutting machinery-equipped vessels. Macrocytic has the peculiarity of being the principal seaweed across the globe. The biggest attached plant ever recorded was 65 meters long with the capability of growing 50 cm daily. Alginate is used in a number of diving industries such as the pharmaceutical and cosmetics sector, although the most prominent of consumers of this compound remain the textiles and food sectors, with a percentage of 50% and 30% respectively. 

The compound is used as ice cream stabilizer in the food industry to make it smooth, and to make it more melt-resistant. It is used by bakers to improve the lightness and succulence of bread loaves, as well as making bread more resistant to drying out. Another application of this compound in the food sector is to add more strength to the production of dried noodles, as well as increasing the yield of the finished product. Alginates also find their way into the confectionery sector in the production of chocolate, soft agar sugar, milk sugar, and other high-quality candies. Algin can increase the melting point of a product when used appropriately, as well as improving its durability and lessening its glueyness. It is used in the beverage industry to decrease precipitate. This compound can also be used for coating as a preservative for fruit, meat, fish, and other foods.

This compound is also an essential component in the textile industry. Only a small amount of alginate is needed to displace a large magnitude of starch. It is also a vital additive and stiffening agent in the dyeing and printing industry and has a number of applications in the medical industry for wound care, and as a growth medium. This excellent material is used as a radiography agent for barium meals, and in the treatment of intestinal diseases, such as gastric disorders and high blood pressure, not to mention its uses as dental impression materials that were discussed earlier.

Algin Extraction and Processing in Making Alginic Acid

Algins are obtained from fresh/wet or dehydrated kelp. The process of extracting the pure material is a complex one. The methods are proprietary with no company revealing its exact methods. But in general, the conventional process of extraction includes the conversion of insoluble salts in the seaweed with an alkali that is readily soluble in water. When the solution is further diluted in fresh water, the cell structure of the algal breaks down, releasing sodium alginate into the solution. Sodium and potassium alginate are the critical agents in manufacturing molding powders that are used in the production of impression material, from where the material derived its name. The insoluble seaweed elements are then separated from the solution using typical solid-liquid elucidation via a centrifuge. The algin is recuperated from the sodium mixture by numerous alternating procedures, which include precipitating it with either sulfuric acid or calcium chloride, direct drying or electrolysis. The acidic effect of alginic is then neutralized with a number of bases before being desiccated, pulverized and dried to produce the final powdered product.

The Dental Impression Material Formulation

Alginate molding material formulas consist of a number of ingredients. First and foremost, they contain potassium, sodium or triethanolamine salts, which are the gelling component of prosthetic alginate. These products are categorized as irreversible hydrocolloid because they contain elements in a jellylike (colloidal) state in water (hydro) which irrevocable because as soon as the solution has thickened, it cannot be reverted to the liquid state.

Ross ribbon mixer

Figure 3. Stainless steel ribbon blender used to mix 500-pound batches of prosthetic grade impression material. The various ingredients are added from the top. After thorough mixing, the blended impression materials drop out of the bottom of the blender.

For strength diatomaceous earth (DE) is added. This is sourced from the alluvial deposits of skeletal remains of algae diatoms (Bacillariophyceae). These prehistoric single celled creatures were active in both freshwater and saltwater as well as in the soil. These remnants then form a diatomite in a pure virtual state of silica which is then grounded into a grainy powder. It is predominantly silicon dioxide (i.e., glass, sand).  

The formula for a prosthetic grade impression material comprises more than 15% of sodium or potassium alginate. In addition to the diatomaceous earth, a calcium source such as tetra-sodium pyrophosphate is added as a retarder to slow the curing time. Then a pH converter such as magnesium oxide or potassium fluorinate is added.

Formulations for life-casting (i.e., prosthetic grade) impression materials differ significantly.

The formulas that the body casting artists and mold makers use are typically manufactured to dental grade standards but adjusted for lengthier set periods and shrink proportions, and tear strengths.

Prosthetic Grade Impression Material Use in Lifecasting Artistry

Due to the safety history behind its usage, first as a dental impression material as well as a prosthetic limb mold building material, algin was first discovered by early life-casting artists who used them for mold making directly from the human body. Before the advent of this material, life molding was produced from gypsum plaster. However, due to its build up of heat during curing it caused injuries. However, prosthetic grade creams are water-based material and are entirely harmless, as they produce no heat. In fact, due to its relaxing feature, it is employed in facial treatments at day spas.                  

Features

Another interesting fact about prosthetic grade cream is that once set, a second coating will not adhere to the first coat. That same distinguishing factor is beneficial in lifecast mold making, just like Teflon that doesn’t stick to anything, excluding the stainless-steel jiffy mixer. However, if you want it to stick to itself, all you have to do is increase the surface pH which can be easily achieved by painting its surface with a blend of baking soda and water or spray it with ArtMolds Algislo. Once this is done, coat the surface again with prosthetic grade alginate to overlay the first coat.

To adjust the set time for prosthetic grade cream, vary the water temperature, and that will do the magic!  The higher the water temperature, the thicker the mixture, and the quicker the curing effect and vice versa. Nevertheless, since lifecasting involves applying mold material to the skin of a living being, cold water and mold material generates goose bumps and can make the model uneasy,  so keep that in mind.

The Quality of the Water is Very Important

The quality control departments of all the manufacturers control their blending formulation by carrying out quality testing. Every batch of the prosthetic grade impression materials produced is tested using deionized water, distilled or soft water. Excess mineral content in will lead to an unsmooth mixture, slightly similar to cottage cheese, which will create a poor mold surface.  Extremely hard water will not allow the impression material formulas to cure evenly. Ordinarily, the tap water from the city water works is neutral enough to make a smooth mixture.

Experienced artists always test small batches of the formulation when attempting a studio mold to eliminate any uncertainty, and to avoid a failed mold making session. So, if you are in doubt, make use of bottled or distilled water, as poor water quality is the deciding factor in the success of many casting sessions. It is important to take note of the water quality before proceeding with a mold making mix.

Although the manufacturer has controlled the quality of the formula, it is the responsibility of the user to control the water quality. Perfect ratios of water-to-impression material differ from one manufacturer to another and the personal preference of the user. So, we recommend that each artist experiments first to determine the proportions that will produce the best mix. For instance, a thicker uniformity would be required to create a mold in a vertical position to avert excessive run off due to drippin

.Alginate Weaknesses as a Mold Making Material

For every advantage a product offers, there are also disadvantages. As good as prosthetic grade impression material is when it comes to mold making, it also has its shortcomings.  One shortcoming is that an alginate mold can only be used once. It is therefore known as a waste mold. Alginate molds also tear easily as they only cure to the consistency of a hard-boiled egg. Thus, the material is not strong enough to withstand multiple casting tears, although brands like ArtMolds FiberGel, strengthened with fiber, can survive a number of castings because of its excellent tear strength.

Additional characteristics of prosthetic grade impression material is that the mold starts to shrink as soon as it sets, losing detail in a couple of hours and losing up to a third of its size within twenty-four hours. Nevertheless, placing the mold in a plastic bag or container with a wet rag or sponge will suspend the shrinkage thereby extending the casting period.

The mold maker is also restricted to a limited choice of casting materials with prosthetic grade cream molds. Although silicone rubbers, plasters, and waxes are excellent casting choices, resins are not. That is because polyurethane and polyester resins respond poorly to the wetness in the mold and will foam up when in contact with moisture.

artmolds alginate line

Figure 4. The ArtMolds line of prosthetic grade cream products. From left to right. MoldGel Regular Set (4-5 minutes setting) SILFREE (contains no silica); MoldGel SloSet Set (7-8 minutes setting) SILFREE (contains no silica); Hollywood Impressions (2-3 minutes setting) SILFREE (contains no silica); FiberGel Highly Tear Resistant (5-6 minutes setting); Algislo Alginate Bonder, Cleaner, Retarder; MoldGel Regular Set (4-5 minutes setting) Traditonal Formula; MoldGel SloSet Set (7-8 minutes setting) Traditonal Formula; Hollywood Impressions (2-3 minutes setting) Traditonal Formula.

Personal Experience by a Master Lifecasting

The late Dave Parvin, fine art sculptor, lifecasting teacher and frequent contributor to the Art Casting Journal, describes his experiences.

“Years ago, I developed a solution that I have used with great success and taught in all my workshops – I felt then it was perfectly adequate. I would apply a layer of alginate that was just the right consistency and temperature to stay in place and be comfortable and allow enough time for a flawless second layer into which I would embed the fuzzy material. The trick is to paint over the first layer with a mild base such as solution of baking soda and water without which the layers would not bond together. With this technique I have been able to do far more complicated castings than would be otherwise possible. The only downside was the extra time cost required for the second layer.”

“Particular brands are for the most part simply a matter of personal choice since most are pretty much interchangeable. However, most alginates have the same characteristic in that they exist in either a liquid or a solid state with a very short transition stage. For simple casts such as hands or face without hair, ears and shoulders, this poses no problem.”

“But as one progresses to more complicated castings, it becomes very difficult to apply and embed a layer of fuzzy material into the molding material to hold a plaster shell mold fast before it sets-up. While either increasing the ratio of water or lowering the temperature of the water can extend set time, neither of these solutions is adequate. Too runny and the it will not stay in place and too cold is not comfortable for the subject.”

“There is however, another solution. MoldGel Sloset from ArtMolds is uniquely different from any other alginate I am aware of in three ways. The first is that it has the slowest setting time of any I tried, 8 to 9 minutes in warm water. Secondly it is more thixotropic (i.e. it stays in place without running off the model). Thirdly, the transition from a liquid to a solid is far more gradual. The result is that one can apply an adequately thick layer that stays in place even in undercuts such as below the ears, breasts, chins, etc. and on small pointy places such as noses, nipples, finger tips, etc. This eliminates, for the most part, the need to keep applying additional material to hard-to-cover areas. This time saved along with the slower setting time allows the caster to apply the fuzz before the it gels.”

“In addition, the more gradual gelling further prevents runoffs and indicates to the caster how much time is remaining. Eliminating the second layer reduces the overall time required for the process making it easier on the model. Because there is less runoff, less is wasted and the need for a second layer is eliminated.

We also recommend high strength FiberGel E F/X Grade cream

Let’s Talk About EnvironMolds

In 2018, EnvironMolds celebrated its 20th year of offering ecologically friendly and user-safe mold making and casting materials. Its ArtMolds brand products and kits are sold in fine art and hobby stores internationally. The company as well as its website, www.artmolds.com, offers an archive of DIY articles and videos. These mold making and casting materials are beneficial to the novice as well as the more experienced artist. Using them you will be taught how to virtually replicate anything using EnvironMolds’ assortment of prosthetic grade creams, latex rubber, numerous silicone rubbers, gypsum plasters, polyurethane resins, and associated mold creating and casting materials and tools.

Why You Should Buy from Us

EnvironMolds, with twenty years of manufacturing, has the experience, capacity, and knowledge to help you productively complete your reproduction projects. You don't even need to purchase anything if you just need advice. We also assisting artists and sculptors with our hotline which is available 24/7. As for prosthetic grade cream offerings, ArtMolds offers seven varieties for every mold making application, including MoldGel which is less expensive than most of the other makes, so your mold making cost is reduced by as much as 50%. For these reasons, MoldGel SloSet is my number one choice for everything excluding hands of infants.

Now that you have acquired more knowledge about alginate, it is highly recommended that you experiment with diverse brands as a life-casting artist, because each producer offers distinctive characteristics. Regardless of your choice of brand, you can rely on a product class that will deliver excellent reproduction and the certainty of protection with their model. We are very confident that in the end, you will make the ArtMolds brand your preferred brand, too.

EnvironMolds is very dynamic across all the social media. We especially invite you to follow us by clicking on the respective social link signs below!

Follow Us

EnvironMolds is active on social media. We invite you to follow us. Please click on the social link icons below on the hand right side.

Continue reading

Copyright © 2017 EnvironMolds LLC. All rights reserved.