A further test for judging the quality of rockwool slabs is the Blue Dye method. You will need the following to carry out the test: - Blue food coloring found in most stores
- Similar rockwool block or slab to compare to Grodan
- Whatever hydroponic system you use to wet your rockwool
Steps:
- Pre-wet the rockwool slabs or blocks with plain water and let it drain.
- Make a solution of blue dye. Be careful because it can get messy.
- Irrigate the rockwool products for about 5-10 min but with the same amount of blue dye solution. Make sure to do this in an area that can be easily cleaned up afterwards.
After watering with the blue solution, examine the blocks or slabs. The best media has a darker blue color and best distribution of color throughout the product. A light-blue color signifies that the new plant food ( in this case the blue dye) is not replacing the old plant food very well (in this case the plain water ).
IF, you cannot see a difference, you may not have used enough blue dye in the solution.
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