These small particles are classed as “fine mineral fibres”, which the Environmental Protection Agency (EPA) in the United States has identified as probable human carcinogens  .
The process of making Rockwool cubes also takes a toll on the environment. In addition to the endless quarrying of basalt rock, it takes a considerable amount of coal energy to heat furnaces and power the machines needed to process the whipped-up lava wool.
Some growers like to keep repotting their plants as they grow. However, for the sake of simplicity, we recommend transplanting into a fabric pot and keeping your plants there until harvest. This reduces future transplant stress and keeps plants growing quickly.
Many cannabis growers and businesses are making the switch to more sustainable and environmentally friendly products and methods. The idea of used Rockwool cubes sitting in a landfill site repels some cultivators. Because many growers still don’t make their own compost, and don’t want to go to the effort of shredding up their cubes, this is exactly where many Rockwool cubes sadly end up.
3. After 24 hours have passed, fill up another bowl with 1 litre of water. Add your organic nutrient solution, fungi, and bacteria to the bowl in the quantities stated on the instructions. Soak the blocks in the solution for another two hours.
Rockwool also poses a potential health hazard to growers. New Rockwool cubes can contain a lot of loose fibres and dust. These particles can end up in the air, and even on your skin and in your eyes, mouth, and lungs. Much like asbestos, tiny fibres can build up in the lungs over time if you work with new Rockwool cubes every day.
Yes! Rockwool contains basalt, which works great as a soil amendment in general. Once it becomes weathered over time, it releases nutrients such as phosphorus into the soil.
I use the paper towel method 100 percent success rate for me, then once the little white tail pops out of the seed, then move the seeds to the 1 inch rock wool with the tail facing down in the hole then lightly put a little piece of rock wool over the hole that the seed is in.
seedlings in them you would not have to water for about a week maybe longer.
i would have soaked mine over night first 75 percent of time is split the next day
Professional advice = reputation+
i have a Hydro set up also so i have been starting seedlings in rockwool for years.
Rockwool Cubes are designed to maintain the correct water to air ratio and squeezing them may damage their structure. Some of the marijuana forums advocate doing everything from squeezing them completely dry, all the way to flinging them around like paintbrushes in order to get excess water out. None of that is necessary, leave it as it is. It will stay moist for several days without needing to be watered this way as well.
Most Rockwool cubes come with holes in them, if yours did not, than create a hole in one side that is approximately a quarter inch (0.75 cm) deep.
Important: Do not let the PH of the water go below 5. A Ph this low will damage the fibers of the Rockwool Cube
Get a bowl or some other container that is big enough to fill with water and have room left for your Rockwool cubes. Your average salad bowl will work fine for 3 Rockwool cubes, if you are planning on doing more than you will need a larger container.
Do not add any nutrients to your Rockwool Cubes. The one on the left got nutrients, the other two did not.
Now, if you can, place them in a tray with a dome on it. This will help create a little humidity in there which seedlings like. This is not mandatory, but it helps. Whichever you choose, take your cubes and put them in a cool dark place, and leave them alone. The temperature should be roughly 68 degrees F, though my house stays at about 72 and they do fine there. I usually place them above my refrigerator and just leave them for a day or two. My lettuce seedlings sprouted with a quickness the last time I tried, and by the 3rdday they had grown so tall that I had to take the plastic dome off of my container because they were bumping up against the ceiling.