How to use Rockwool Cubes for Growing, Seed Starting, and Cutting Propagation

Rockwool is a mainstay growing media for commercial hydroponics growers, primarily those who implement drip irrigation systems. Originally used as insulation and also known as mineral wool or stone wool, rockwool was developed in Denmark back in the 1970’s for gardening. It retains moisture well, it retains oxygen well, it never impedes root growth, it is chemically inert, and it comes in a variety of sizes and shapes. These benefits contribute to its popularity amongst growers, accommodating almost any plant they are growing.

What are Rockwool Cubes?

Similar in texture to steel wool, rockwool is a dense mat consisting of long strands of natural fibers. Basalt rock and chalk are combined and then melted at a very high temperature (approximately 3000°F) to form lava. Then people throw the lava into a spinning chamber to create the fibers in a process much like making cotton candy.

Due to the firing process, rockwool cubes are chemically and biologically inert. This creates an ideal growing medium for hydroponic growing systems.

After the fibers are spun, they are mixed with a binding agent and pressed into large mats. The mats are then cut into various sizes of cubes and slabs to be sold to customers as a growing medium for plants.

Rockwool cubes are popular with hydroponics growers, as well as conventional growers because of their beneficial structure. When the fibers are spun it creates a structure that is perfectly suited to retain water while holding more oxygen than typical soil mediums. The increased water holding capacity and oxygenation within the root zone is exceptionally beneficial when starting seeds and rooting propagation cuttings.

Another benefit to rockwool cubes is they are considered to be a natural product even though they are man made. This is because they originate from basaltic rock and chalk which are natural ingredients. Being considered a natural product makes them acceptable in organic growing systems, increasing their popularity.

Their inert nature also means growers can quickly adjust the conditions within the root zone to meet the needs of plants. A non-existent cation exchange capacity (CEC) prevents nutrients from being changed by the growing medium or tied up and made unavailable for plant uptake. The cubes can also be quickly rinsed with fresh water, leaching fertilizer salts out.

Rockwool cubes come in a couple of different sizes. The smallest ones work well for starting seeds and propagating stem and leaf cuttings; the larger cubes are used by growers to grow more compact plants.

Do’s and Don’ts of using Rockwool Cubes

One of the drawbacks to using rockwool cubes is the special care and consideration that needs to be taken when working with them. While they are a beneficial resource for hydroponics growing system, they do have some important drawbacks that need to be addressed.

• DO take the time to properly prepare rockwool cubes before starting seeds or trying to root cuttings. Their natural pH is too high for optimum plant growth and will create problems and instability within the hydroponics system if left at that alkalinity.
• DO wear protective gear to keep yourself safe when handling rockwool material. The fibers are irritating to skin, lungs, and eyes so it’s imperative to protect yourself. At the minimum, wear a dust mask to prevent inhaling fibers into your lungs. It’s also recommended to wear eye protection and long sleeves if there is a chance of prolonged contact with your skin.
• DO sterilize the feeding solution before running it back through the rockwool cubes. Even though it is a manmade, inert material, it can still be prone to algae and bacterial growth that can contaminate the hydroponics system if the feed solution is recirculated without being treated properly.
• DO dispose of the materials properly after you are done using the cubes. Unlike other growing mediums, rockwool is not composed of natural materials so it will not break down over time. If it reaches the landfill it will be there indefinitely. Instead of throwing them away, break up the pieces and work them into your garden or potting soil to help increase their water retention.
• DO heat treat the rockwool cubes if you are going to reuse them for a successive growing season, or even numerous seasons. This can be done by steaming them, or pouring boiling hot water through them to kill off any bacteria or fungus that may be residing with the cube’s fibers. Some websites recommend using chemical treatments to sterilize rockwool cubes to use again but this can be dangerous unless you are absolutely sure you have rinsed all of the sanitizing chemicals out of the fibers.
• DON’T squeeze the cubes when they are wet. If you need to remove some of the water from them after preparing them in a pH controlled solution it’s best to shake them gently. Rockwool cubes are known for their internal structure that gives them such great water holding capacity and oxygen movement; squeezing them compacts the structure and hinders the benefits they are so well known for.
• DON’T forget rockwool is completely inert and can not provide any nutritional value to the plants growing in the cubes. Everything the plant needs has to come from the nutrient solution supplied to them.

How to Prepare Rockwool

Before using your rockwool in a hydroponics system it’s important to prepare it for use. Unlike other pH-neutral hydroponic growing media like Hydroton, and Coco Coir, Rockwool has a naturally high pH, typically around 8.0, because of the way it’s manufactured. During the process there is an abundance of lime that is deposited on the fibers; lime naturally neutralizes acidity, raising the pH.

A pH of 8.0 isn’t optimum for growing plants so it needs to be adjusted to a level that is better suited for growth. A higher pH will make many plant essential nutrients unavailable for plant uptake, causing deficiency symptoms. Most plants prefer to grow in slightly acidic conditions, and will benefit if the pH of rockwool cubes is brought down to a more acidic level.

There are different ways to prepare rockwool for use, none of which are difficult, but they can be time consuming. Due to this you will need to account for a couple of days to prep rockwool before being able to use it.

The first step in preparing rockwool cubes is to soak them in acidic water to lower the pH. The acidic water will dissolve the lime that is formed on the fibers during the manufacturing process and the pH will drop to a better level.

It is best to use distilled water because of its purity but tap water can work in a pinch if it is the only thing available. Adjust the pH slowly until it reaches the desired 5.5; it is critical the pH doesn’t drop below 5.0 since it will start todamage the rockwool fibers when it is too acidic.

After Then submerge the rockwool cubes in the water and allow them to soak for up to 24 hours. When they have finished soaking, remove them from the water and carefully add them to the hydroponics system and allow the system to run without any plants until the pH of the system stays between 5.5 and 6.0 — this means the cubes are stable and can be used.

This video will show you how to prepare rockwool properly.

What are the Uses of Rockwool Cubes

Rockwool cubes hold a tremendous amount of water for their size, which provides a buffer against power outages that make shut down pumps or timers. On average they also hold at least 18% oxygen between the fibers providing a tremendous amount of oxygen to the root zone, as well as making it incredibly difficult to overwater the plants.

Growers primarily use rockwool cubes as growing media for two main purposes in their hydroponics systems: germinating seeds and propagating new cuttings. Typically the 1.5” cubes are used for starting seeds or propagating cuttings. Some of the larger cubes (up to 4”) are used as a growing medium for compact plants as well, but on a much smaller scale.

Germinating Seeds

Starting seeds can sometimes be a stressful adventure. It’s a constant balance between keeping them wet enough to promote germination without having them so wet they dampen off and die. Rockwool cubes are popular for germinating seeds in because of their excellent moisture retention — they are great at helping to keep seeds or seedlings from drying out but don’t let them sit in a waterlogged environment.

Moisture is the critical factor in seed germination. Water enters the seed through the seed coat or tiny opening called a micropyle. The presence of water will activate the enzymatic reactions within the seed that begin germination.

Cloning New Plants

Propagating new plants is the process of taking an existing plant part (usually a leaf or stem cutting) and growing it into a whole new plant. This method results in an identical clone of the original and is cheaper than purchasing seeds and starting from scratch.

Maintaining a high humidity around the cutting is critical for successful propagation. Plants need to keep from drying out; without enough moisture the plant will go into self-defense mode and will stop trying to develop new roots.

Growing new plants through propagation techniques needs to happen in a sterile environment, free of bacteria or fungus. Rockwool cubes are completely inert because of the heating process they undergo during manufacturing. This ensures they are sterile and free of any harmful microorganisms that could hinder propagation.

Step by Step Instructions Using Rockwool for Seed Plantings and Propagating Cutting

1. Prepare the rockwool cubes for use, making sure to soak them in pH adjusted water to bring their pH down between 5.5 and 6.5.
2. To Plant Seeds:
   1. Insert 2 seeds in the hole on the top of the rockwool cube. Use a toothpick or other similar object to press the seeds down to the bottom of the hole.
   2. Pinch the hole closed.
   3. Place the cubes in a nursery tray and cover with a humidity dome to lock in moisture.
   4. Maintain at 70 – 80°.
   5. Keep rockwool cubes moist by watering sparingly every couple of days or misting with a spray bottle when they start to dry out.
   6. Remove from humidity dome and place under lights as soon as seeds sprout.
   7. Cut the tops off the seed in each cube (if you planted 2 per cube) that isn’t the strongest or tallest. Do not pull them out as it may dislodge the healthier plantlet at the same time.
   8. Transplant when plantlets reach 2-3” in height.
3. To Propagate Cuttings
   1. Water the stock plant well the night before beginning the propagation process.
   2. Remove a 3-4” leaf stem cutting from the main stem of the plant, cutting it off as close to the main stem as possible without damaging the node.
   3. Dip cut end in rooting hormone.
   4. Plant the cutting in the rockwool cube making sure it doesn’t poke out the bottom of the cube.
   5. Fill a nursery tray part way full with perlite or vermiculite.
   6. Set rockwool cubes on top of growing media.
   7. Cover nursery tray with a humidity dome to lock in moisture.
   8. Maintain close to 80°.
   9. Crack humidity dome when roots begin to emerge, gradually increasing the day after.
   10. Remove the humidity dome a couple of days after roots first appear.
   11. Transplant when roots begin to poke out the bottom of the cubes.

Conclusion

Rockwool cubes are an indispensable product in the hydroponics growing industry. Naturally occuring basaltic rock and chalk are melted down at really, really high temperatures in a molten lava. This lava is then put into a spinning chamber to create long fibers that are later formed into blocks or cubes for easy handling. Rockwool cubes are popular because they retain moisture and oxygen well and they never impede the development of roots. With a variety of sizes and shapes available, they are adaptable to almost any grower’s setup.

by Max  www.trees.com

China's national rock wool external wall thermal insulation standard is higher than the European standard in terms of technical requirements

 China's national rock wool external wall thermal insulation standard is higher than the European standard in terms of technical requirements

■Zhang Jianhong, Director of Thermal Insulation Material Testing Center of Nanjing National Materials Testing Co., Ltd.

2021-05-13

With the continuous innovation and development of enterprises, the technical index of the rock wool national standard for external wall insulation in China are higher than the European standards. At the same time, through continuous improvement of production technology and equipment, the product quality of domestic standard enterprises fully meets the standard requirements, and some enterprises have even reached the international advanced level.

How to ensure the quality of rock wool products and how to ensure the construction quality of the project are all issues that we need to pay attention to. Therefore, in the construction process, we must first ensure that qualified products are used, and secondly, strengthen the supervision of construction. As the saying goes, "30% of materials and 70% of construction", only when the materials meet the standards and the construction meets the requirements, the problem of the external thermal insulation system of rock wool can be eliminated. Thus, two suggestions are made: First, all materials used in the external wall insulation system should have their own logos, with LOGO on the products, refuse to use "unlabeled, unnamed, uncertified" products, and ensure that they are qualified products from the material. Secondly, strengthen the professional training of domestic rock wool external wall insulation system builder, reduce the problem of falling off due to non-standard construction, and ensure professionalism in construction.

Rock wool external wall thermal insulation system has excellent thermal insulation performance and anti-aging, weather resistance and fire resistance performance. It has been successfully used in Europe for decades and has become the main form of building thermal insulation and energy saving in Europe, especially for high-rise buildings. The use of rock wool insulation system, which has only been developed in China for about 10 years, is still in its start-up stage. In recent years, our real estate industry has developed rapidly, among which the proportion of high-rise buildings is relatively high. Therefore, there is still a lot of room for development of the external wall insulation system of rock wool Class A fire protection. As a kind of external wall thermal insulation material with excellent comprehensive performance, rock wool will become an indispensable energy-saving thermal insulation material in the process of successfully achieving the carbon peak and carbon neutrality goals in China as long as we can correctly understand and apply it correctly.

Introduction of rock wool standard

European rock wool standard

The technology of using rock wool for external thermal insulation of building exterior walls originated in Europe and has a history of several decades, especially its application in Germany is very mature. Therefore, the European standard system for external thermal insulation rock wool for building exterior walls is very complete. At present, there are mainly EN 13162 "Insulation products for construction-Mineral wool products produced in factories-Specification", EN 13500 "Insulation products for construction-Mineral wool base exterior E
xternal Thermal Insulation System-Specification, ETAG 004 "Exterior Thermal Insulation Composite System with Plastered Surface-European Technical Certification Standard" and German External Thermal Insulation Association FV WDVS "Technical Regulations for Rock Wool External Thermal Insulation System". Except for EN 13162, which is a standard for rock wool products, the other three are standards for external wall insulation systems. These three system standards all put forward requirements for the performance of rock wool products, but the requirements are not the same. EN 13500 proposes six performance requirements for rock wool: thermal resistance, size, tensile strength perpendicular to the surface, dimensional stability, compressive strength, and long-term water absorption; ETAG 004 proposes thermal resistance, water absorption, and vertical to rock wool There are six performance requirements for surface tensile strength, shear strength and shear modulus, moisture permeability and combustion performance; the FV WDVS technical regulations of the German External Insulation Association put forward the size, thermal conductivity, and resistance perpendicular to the surface of rock wool. There are 7 performance requirements for tensile strength, compression strength, shear strength and shear modulus, combustion performance and moisture permeability. The requirements of EN 13162 for rock wool are divided into general requirements and specific requirements, of which there are 4 general requirements, including: thermal resistance and thermal conductivity, size (length, width, thickness, right angle deviation and flatness), combustion performance, durability (That is, the combustion performance, thermal resistance and thermal conductivity do not change with time); there are 17 other specific requirements, including: dimensional stability, compressive strength, tensile strength perpendicular to the surface, point load, compressive creep, short-term water absorption, long-term Water absorption, moisture permeability, dynamic stiffness, compressibility (for floating floor slabs), sound absorption performance, airflow resistance, hazardous emissions, product combustion performance in standardized assembly when simulating terminal applications, continuous luminous combustion, shear stress, bending stress.

From the analysis of the above several standards, it can be seen that the system standard has fewer requirements for the performance of rock wool, only some key performance requirements, and the product standard EN 13162 features: First of all, no specific index are proposed for all performances, but it is sufficient to meet the nominal value; secondly, there are fewer general requirements, and specific requirements do not indicate specific application occasions, and specific requirements index need to be proposed by enterprises or users.

 

Domestic rock wool standard

After 20 to 30 years of development, the domestic rock wool standard system is relatively complete, mainly including GB/T 11835 "Rock wool for thermal insulation, slag wool and their products", GB/T 19686 "Rock wool thermal insulation products for construction" GB /T 25975 "Rock wool products for external thermal insulation of buildings", JC/T 2292 "Rock wool products for fire isolation belts", JGJ/T 480 "Technical standards for external thermal insulation of rock wool thin plaster walls", JG/ T483 "Rock wool thin plaster external wall external thermal insulation system materials", the first 4 are rock wool product standards, of which GB/T 11835 is mainly applicable to industrial thermal insulation rock wool products, and GB/T 19686 is applicable to external walls except for thin plastering Rock wool products for other applications in the construction field of external thermal insulation, GB/T 25975 is suitable for rock wool products for external thermal insulation of thin plaster walls, and JC/T 2292 is suitable for rock wool products for fire isolation belts. JGJ/T 480 and JG/T 483 are external wall external thermal insulation system standards. The system standard only proposes some key performance index for rock wool products. Compared with the system standard, GB/T 25975 is the external wall thermal insulation rock wool product standard. The requirements for rock wool products are more comprehensive. When the standard was drafted and formulated, the two standards EN 13500 and EN 13162 were mainly referred to. In addition, many performance index that were not in the European standards were added on this basis. Therefore, compared with the two standards of EN 13500 and EN 13162, GB/T 25975 has higher requirements for rock wool products.

GB/T 25975 proposes 17 general requirements for external wall thermal insulation rock wool, namely appearance, average fiber diameter, slag ball content, density, size (length, width, thickness, right angle deviation and flatness), acidity coefficient , The sum of potassium oxide and sodium oxide content, dimensional stability, mass moisture absorption rate, water repellency rate, short-term water absorption, volume water absorption rate (full immersion), thermal conductivity, tensile strength perpendicular to the surface, compressive strength, shear Strength and shear modulus (bar), combustion performance; 3 special requirements: moisture permeability, long-term water absorption, retention of tensile strength perpendicular to the surface, and specific technical index for these 20 performance requirements .

  

Comparison of rock wool standards

From the comparison of the performance requirements of rock wool, the national standards are more than the European standards; from the performance requirements, the national standards are not lower than the European standards (see Table 1 for specific comparison).

In the performance requirements of Table 1 above, the average fiber diameter and slag ball content are important parameters to characterize the fiber formation rate of rock wool. The finer the fiber diameter, the more the number of fibers; the less the slag ball content, the more the number of fibers. For rock wool of the same density, the higher the fiber-forming rate, the more fiber it contains, the better the thermal insulation effect. National standards set requirements on the average fiber diameter and slag ball content, while European standards have no requirements.

The acidity coefficient is a unique index of Chinese standard, and the level of this index reflects the durability of rock wool. In China, due to the rich resources of slag and the low price, adding slag during production can lower the melting temperature, so part of the slag is added when producing rock wool. However, adding too much will decrease the durability of rock wool and become slag wool. Slag wool is not as good as rock wool in terms of stability and fire resistance. It has high requirements for service life and fire resistance when used on building exterior walls, therefore, the standard stipulates that the acidity coefficient must meet the requirement of higher than or equal to 1.8 , So as to ensure the durability of rock wool used for external wall insulation. European standards do not require this.

Waterproof performance is one of the most important properties of external wall insulation materials. In national standards, five index such as water repellency, mass moisture absorption, short-term water absorption, long-term water absorption and volume water absorption are used to strictly assess the water absorption of rock wool. The problem is to ensure that the rock wool used for external insulation of external walls must have excellent waterproof performance. In European standards, there are only two index of short-term water absorption and long-term water absorption to assess the water absorption performance of rock wool. National standards for short-term water absorption requirements are: rock wool board water absorption is not more than 0.4kg/m2, rock wool sliver is not more than 0.5kg/m2; long-term water absorption requirements are: rock wool board is not more than 1.0kg/m2, rock wool Article is not more than 1.5kg/m2, the European standard short-term water absorption requirement is not more than 1.0kg/m2, and the long-term water absorption requirement is not more than 3.0kg/m2. By comparing the water absorption index requirements, it can be seen that the national standard is obvious higher than European standard requirements.

Mechanical properties are an extremely important safety performance index in the application of external wall insulation materials, and the tensile strength perpendicular to the surface is particularly important. The national standard has four grades of tensile strength of rock wool: TR7.5, TR10, TR15 and TR100, and the European standard has several grades such as TR5, TR7.5, TR14, TR15 and TR80. It can be seen that the national standard’s resistance-the tensile strength grade is not lower than the European standards, especially in the lowest and highest grades, the national standards are higher than the European standards. In terms of compressive strength performance requirements, the national standard has two requirements of 20kPa and 40kPa, and the European standard has three requirements of 5kPa, 10kPa and 40kPa. It can be seen that the national standard is not lower than the European standard. In terms of shear strength and shear modulus
requirements, national standards are consistent with European standards.

Combustion performance is the most concerned safety performance index in the application of foreign wall insulation materials in recent years. The national standard requires the combustion performance of rock wool to be A1, which is also the highest level of combustion, which is equivalent to the European standard EN 13501-1 "Construction Fire classification of products and components Part 1: Class A1 in "Classification of test data using reaction to fire". The three European standards EN 13162, EN1 3500 and ETAG 004 require the combustion performance of rock wool to meet the requirements of A1-F in EN 13501-1. That is to say, the company only needs to comply with which level it claims. There is the German Association of External Insulation FV WDVS, which requires the combustion performance of rock wool to comply with A1 in EN 13501-1, which is the same as the requirements of Chinese standard.

The retention rate of tensile strength is the ratio of the tensile strength of rock wool to the untreated tensile strength after being treated for a certain period of time under certain temperature and humidity conditions. It is an important parameter that characterizes the retention of mechanical properties and durability of rock wool after high temperature and high humidity treatment. . In the national standard, the retention rate is not less than 50%. In the European standard, only ETAG 004 mentions the tensile strength after the test treatment, and the other standards do not mention this requirement.

It can be seen from the above comparison that national standards are not lower than European standards in terms of the number of performance requirements or quantitative index, and some are even stricter and more demanding than European standards.

Quality analysis of domestic rock wool products

Since 2010, after several major fires occurred in China, Class A fireproof materials have been favored by external wall insulation, among which rock wool has emerged from various thermal insulation materials. Since then, rock wool companies have sprung up one after another, and their production capacity has increased rapidly.

With the rapid development of the rock wool industry, there have also been some chaos in the rock wool industry. Some rock wool and slag wool of various qualities have acted as GB The products required by the /T 25975 national standard are being sold and used. In order to cope with the chaos in the rock wool industry and to promote the high-quality development of the rock wool industry, a national rock wool product quality sampling activity was carried out in 2013. The purpose is to conduct a thorough investigation of the technical level and product quality of domestic rock wool manufacturers and guide them. Enterprises continue to improve the level of production technology and product quality. This activity is voluntary for enterprises to participate in.

According to the requirements of sampling inspection, the samplers come to the enterprise to conduct random sampling, and then conduct inspections in accordance with national standards, and finally issue inspection reports. In 2013, 24 enterprises participated in the activity, involving 7 provinces and 3 municipalities, 33 batches of sampled products, 27 batches of qualified products, and the qualified rate of sampled products was 82%. Since 2013, the activity has been ongoing, and the number of participating companies is also increasing. In 2020, there were 31 rock wool production companies participating in the activity, and 122 batches will be sampled, distributed in 15 provinces and 2 municipalities, from 2014 to 2020. The qualified rates of sampled products are respectively 97%, 98%, 97%, 93%, 91%, 92%, 93%, and the qualified rate of sampled products is basically stable above 90%.

It can be seen that the national rock wool product quality
 sampling activities have been carried out continuously. It has greatly promoted the quality of rock wool products. In addition, the analysis of the sample product qualification rate for 9 years also fully shows that the quality of most of the participating enterprises fully meets the requirements of national standards, and some key technical index are even better than standard requirements, some products have reached the international advanced level.

In addition to the above-mentioned production companies that participated in the national rock wool product quality sampling activities, there are also some companies that did not participate in the activities, and their product quality needs to be focused on. Through the nationwide random inspection of rock wool product quality, we realize that most of the rock wool production enterprises participating in the activity are large-scale and standardized enterprises. Therefore, we also appeal to the majority of users to give priority to the rock wool industry when choosing products. For the products of representative manufacturers in China, a list of rock wool manufacturers that have participated in the national rock wool product quality inspection activities for 5 consecutive years or more and qualified for the random inspection is attached to this article (for reference only).

The above content collected and translated by Nanjing Hairui Insulation Technology-specializing in mineral wool production line building and optimizing, machine and spare parts.

Hairui Insulation Technology:

1.Provide new rock wool production line(mostly 1.5-4 tons/hour, i.e. 10,000 tons-35,000 tons/year).

2.Upgrade and optimize existing rock wool production line.

3.Provide rock wool machinery and spare and wearing parts(such as saw blades, spinning machine roller parts, customized parts) at favorable price.

Website: www.rockwoolmachinery.com             Email: zhao@rockwoolline.com