This sub-board covers concentrates made without a solvent. Instead of a chemical such as ethanol or butane, they use only water, ice, heat and pressure. The main methods are:
- Ice water extraction, which produces bubble hash. You stir plant material in ice-cold water, and the resin breaks off and is caught in mesh bags. The detailed guide is Ice Water Extraction and Bubble Hash.
- Dry sift. You shake or rub dried material over fine screens without water, so the resin falls through. See Dry Ice, Dry Sift and Charas.
- Rosin. You press flower, dry sift or hash between two heated plates, and the resin melts out as an oil. The detailed guide is Rosin: Solventless Extraction with Heat and Pressure.
What these methods actually do
All three methods are mechanical separation. They only sort what is already in the plant. Nothing is added, so the finished hash or rosin cannot be better than the material you started with.
What you collect are the resin heads. These are the small round tips of the trichomes, the tiny resin glands on buds and sugar leaves. They hold most of the cannabinoids and the aroma compounds (terpenes, explained in Terpenes in Cannabis).
A wash uses stirring and sieving to separate intact resin heads from leaf and stem. A press then melts and squeezes what the wash or sift collected. If the heads were already broken or damaged, neither step can repair them.
That is why these methods give the best results from material that is fresh, cold, well grown and handled gently. Material that is mouldy, over-dried or handled roughly gives poor hash and poor rosin.
What to do: before you plan any wash or press, look at your buds under a loupe or phone macro lens. Check that the trichome heads are still round and whole. This tells you whether the batch is worth washing at all.
The two things that matter more than technique
1. Genetics and freshness. The plant variety and how fresh the material is set both the yield and the quality grade before the first bag goes into the bucket. Some varieties release their resin heads easily in water; others do not. For this reason, fresh frozen material is now the normal starting point for a quality wash. Fresh frozen means buds frozen right after harvest, without drying, so the resin heads stay firm and intact.
What to do: keep a short record for each variety you wash, with the weight of material in and the weight of hash out. After a few runs you will know which plants are worth growing for hash.
2. Temperature control at every step. Heat damages the result throughout the process. If the wash water gets too warm, or the press plates are too hot, you may get more weight. But you lose the aroma compounds in exchange, and the product smells and tastes flat. The two detailed guides linked above give the working temperatures for the wash and the press.
What to do: put a thermometer in the wash water and check the plate temperature on the press every run. Write both numbers down next to the yield, so you can see which settings gave the best aroma.
Translator’s note: in Thailand and Southeast Asia, temperature control is the hardest part. Room temperatures of 30–35 °C warm the water quickly, so you need more ice than a grower in a cool climate, and you should work in the coolest room you have or early in the morning. A reliable ice supply and a freezer large enough for the whole harvest must be in place before harvest day, not after.
Translator’s note: fresh frozen material only works if it stays frozen. A power cut that lets the freezer thaw and refreeze will damage the resin heads, and the batch may no longer be worth washing. If power cuts are common where you are, keep the freezer closed, freeze in smaller bags and wash soon after harvest rather than storing for months. In the rainy season, high humidity also raises the risk of mould on buds before and after harvest. Mouldy material should not be washed or pressed; see Mycotoxins on Cannabis Flower for why.
The Thai legal position
Translator’s note: cannabis flower (ช่อดอกกัญชา) is a controlled herb under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, in force since 26 June 2025. Under the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569, in force since 26 April 2026, extracts with more than 0.2% THC can be licensed only to Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, to state agencies and to the Thai Red Cross Society. This article does not settle whether hash, dry sift or rosin count as “extracts” under this regulation, so ask the licensing authority before you make any. Unlicensed processing of a controlled herb carries a penalty under Section 78 of the Thai Traditional Medicine Protection Act B.E. 2542 of up to 1 year in prison and/or a fine of up to 20,000 baht. Read Thailand’s Two Ministerial Regulations of B.E. 2569 and check which licence covers your work before you make any concentrate.
Where to start
- Read Ice Water Extraction and Bubble Hash to learn what separates a good wash from a bad one.
- Read Rosin: Solventless Extraction with Heat and Pressure to learn how to press flower, sift or hash.
- Start with a small test batch from one variety, record temperatures and yields, and post your results or questions below this topic so other growers can compare.