Bubble hash: Fresh-frozen vs dry flowers

Comparing two techniques of hashmaking

In this article, we will be examining and comparing the two most popular approaches to making ice water hash, bubble hash or Ice-O-Lator from cannabis buds: In the first two extractions, we will be using fresh-frozen material to make the hash, while the second two extractions will be carried out using dried, cured flowers.

Dried and cured cannabis flowers

Dried and cured cannabis flowers

Fresh-frozen cannabis buds

Fresh-frozen cannabis buds

The goal of this experiment is to examine the differences in both yield and quality between these two approaches and determine the pros and cons, as each one has its advocates and detractors. Many hash-makers claim that processing fresh-frozen plant material offers greater yields and higher terpene content, while others maintain that using dried material results in a more stable and longer-lasting product, less prone to degradation over time. The fresh-frozen approach can also be useful if you don’t have sufficient time or space to hang and dry your plants, but dried flowers will occupy less volume in the freezer than fresh-frozen material, being less bulky and heavy.

The Experiment

To make sure that the comparison between the two different extraction methods is as fair and even-handed as possible, the flowers we will be comparing are from the same plants, two different phenotypes of the variety R-Kiem from Spanish seed bank R-Kiem Seeds, specialists in breeding genetics highly suitable for extractions. Each plant was processed separately both in its dried and its fresh-frozen form, meaning a total of four different extractions for comparison purposes.

R-Kiem bud maturing outdoors

R-Kiem bud maturing outdoors

Both plants were grown outdoors in full sun and the flowers were collected when fully mature toward the end of October.

At harvest time, approximately half of each plant was trimmed and frozen immediately while the other half of each plant was trimmed and hung to dry slowly in the dark at 50-60% RH/13ºC over the course of a month. Once dry, the buds were transferred to ziplock bags and stored in the freezer for another month before processing.

The same equipment and techniques are used when processing fresh-frozen or dried material, the only difference being that dried flowers will need to be rehydrated before starting the extraction. This is to ensure a cleaner end product, avoiding any contamination of the hash by plant debris that could result from agitating dry and brittle flowers. It’s usually enough to let the material soak in ice-cold water for around 20-30 minutes before proceeding with the extraction process.

Here we’ll just share a few details of the extraction, but for a much more in-depth guide on making your own bubble hash, read our other article on the subject: How to make ice water hash.

The process of making ice water hash

The process of making ice water hash

Extraction process

In this case, the material was processed in a medium-sized portable washing machine, but smaller and larger machines are available depending on your need. Hand-stirring in a bucket is a perfectly viable option for smaller quantities or if you don’t have a washing machine.

Various types of quality and sizes of filter bags are available for making hash, but for this project we used a 5-bag set of Pure Extract Bags to filter the water and separate the vegetable matter (220) and the different sizes of trichome heads by micron size from (160>120>73>25). The use of a 220 micron zip-close work bag inside the machine can be a useful idea to save time and mess, while some may prefer to wash the material loose, thus allowing it to circulate freely in the water. It’s a personal choice and experience will show which works best for you.

For each of the four extractions, we carried out multiple washes in order to separate the maximum amount of resin from the material; first we ran the washing machine for three minutes before draining, separating and collecting the trichome heads, next we washed for six minutes, then nine, 12 and finally 15 minutes each for the last few washes, until the temperature of the water rose above 1ºC and the quality and quantity of the resin collected visibly declined and we decided further extraction wouldn’t yield much of any worth.

Collected resin after a few days in the freezer

Collected resin after a few days in the fridge

After collection, even at an ambient temperature of 10ºC the resin (in particular that of the fresh-frozen material) was far too sticky too break up for drying, so it was transferred to the freezer for a few days to harden it before we micro-planed (grated) it into a powder, thus facilitating drying, which took place in a fridge over the course of two weeks. After another week in a relatively dry, cool room (50%RH/10ºC), the hash was collected for storage in glass jars, the ideal moment to weigh, evaluate and compare the results of each of the different extractions.

Comparing the yield

While we were unable to weigh the now dry buds while they were still in their freshly cut state, as a general rule fresh material will lose around 70-75% of its weight in moisture as it dries. So, with this experiment, we can expect the hash yield to reflect this, with dried buds giving a higher yield percentage by weight than the fresh-frozen material.


This theory was proved to be correct once the dried hash samples were weighed and recorded, as illustrated in this chart, which shows a clear difference in yield between the fresh-frozen and dry material, with the dried flowers delivering approximately twice the return by weight.


However, by adjusting the results to take into account the weight of water lost by drying the buds, we can get a much clearer and more balanced idea of the actual return obtained from the material used. In this case we assumed a weight loss of 70% in the process of drying the flowers, so we reduced the weight of the fresh frozen material accordingly in our calculations to arrive at the figures in the chart on the right, where we can clearly see a spectacular yield from the fresh-frozen extraction of  R-Kiem #1, almost double the yield of R-Kiem #2. We can also see that there’s very little difference between the yields achieved using the dry material of both plants.  So now we know the relative yields, but to properly contrast and compare them, next we’ll have to look at the quality of the hash produced.

Visual comparison of hash from dry material (above) and fresh-frozen (below) of R-Kiem #1

Visual comparison of hash from dry buds (above) and fresh-frozen (below) of R-Kiem #1

Contrasting quality

As we’ve seen, over the two plants the fresh-frozen extraction yielded more weight, but what the charts don’t show us is that it also produced a considerably higher quality and more flavourful resin than the dried material, with the first few washes having a notably lighter colour, and much more of a greasy texture, while later, during the necessary “field tests” the dried, cured hash from the first wash fully melted to liquid when heated on an electric nail at 260ºC, leaving virtually nothing after evaporation, while even the very best grades of the hash made with the dried flowers left behind a small amount of residue when melted on the nail.

Sizes of resin heads in RK 1 F/F extraction

Breakdown of trichome sizes in the R-Kiem #1 fresh frozen extraction

Summing up the quality, by far the best results came from the first few washes of the fresh-frozen material, which produced a hash of truly superior quality, while in general the extraction from the dried, uncured flowers produced resin of a slightly lower grade, but that remained more consistent in quality over multiple washes, not deteriorating and releasing chlorophyll as fast as the fresh-frozen material does.

Other factors to consider

As a personal preference, in the majority of cases, these particular hash makers prefer to work with dried, uncured flowers, but occasionally, with certain, special plants, we’ve found that fresh-frozen material can deliver spectacular results both in quality and weight, but it depends on certain factors.

First wash of Fresh Frozen RK #1

R-Kiem #1 Fresh Frozen 1st wash

In our search for hash producing phenotypes, after we’ve selected plants based on the usual criteria of ease of growth, structure, aroma, effect, yield, etc, then the selection process is all down to how much, how easily and how quickly the flowers will give up their trichomes during washing.

In our experience, most plants will need several washes to get to the point where we feel like we’ve removed the vast majority of the resin heads off the flowers, and we’ve found that as a general rule (of course, there are always exceptions) dried flowers will hold up better and produce cleaner resin over multiple washes, while fresh-frozen material can degrade quickly, releasing chlorophyll as it defrosts during washing, and lending an unattractive green tinge to the resulting hash. A great example of this is our cup-winning cut of Tropical Snow from Danish seed bank Zen Seeds, a plant that produces massive yields of full-melt quality hash up to and beyond the eighth wash when using dried flowers, but when using fresh-frozen material, only the first and second washes are anywhere near the quality we’re looking for.

On the other hand, one occasionally finds plants that are capable of dropping almost all of their trichomes in the first wash, making a second wash a mere formality. We once had an incredible, now sadly lost phenotype of Blue Cheese from Barney’s Farm that did just that, and with incredible aroma flavour and effect too. Plants like this are, in our opinion the perfect plants for fresh-frozen water hash, giving blonde, terpene-rich, top-shelf extracts and impressive returns with very little washing, before the material has any chance of defrosting and contaminating the hash.

First wash RK #2 from dry flowers

R-Kiem #2 1st wash using dried buds

Selection is the key

If this experiment has shown us anything, it’s that the plant material itself will dictate the best way to extract, and it’s really only by trying and testing that we are we able to uncover this knowledge. As we’ve seen with here, there can be notable differences even between phenotypes of the same plant, with the R-Kiem #1 giving almost 100% more yield than R-Kiem #2 in fresh-frozen, but only 23% more with dry material. Not only that, but the #1 phenotype also released almost no chlorophyll during the fresh-frozen extraction, giving a beautiful light-coloured resin, whereas the extraction using dried material of the same #1 plant was visibly darker, having taken on some vegetable matter at some point during the process. And, just to prove how important hash making is for plant selection, and vice-versa, the #2 phenotype behaved in exactly the opposite way, the dried material produced a much cleaner result than the fresh-frozen extraction, from which the third wash and all subsequent washes were, in our view, far too green in colour.

So, at the end of this particular experiment, we’ve seen that from two plants of the same strain that were very similar in appearance, aroma and flower yield, we achieved quite contrasting results from each different extraction process, with R-Kiem #1 being better suited to fresh-frozen hash making, and R-Kiem #2 better suited for extractions using dried material. However, given the considerably higher yields and superior quality obtained by R-Kiem #1 in the fresh-frozen extraction, in this case, we would definitely be keeping a mother plant of that particular phenotype in order to provide clones for future cultivation with hash-making in mind.

Hash jar after thorough field testing

We’d like to encourage you to do the same thing, get your hands on some great seeds and pheno-hunt a great hash plant for yourself, it’s a highly rewarding process and besides, carrying out a thorough assessment and “field-testing” the results with friends is a lot of fun too!

Happy hashing!


32 comments on “Bubble hash: Fresh-frozen vs dry flowers

  1. Grass Chief

    The fresh-frozen approach can also be useful if you don’t have sufficient time or space to hang and dry your plants. On the other hand dried flowers will occupy less volume in the freezer than fresh-frozen material, also being less bulky and heavy.

    1. Dani Alchimia

      Hi Grass Chief,

      That’s correct. Apart from that, I’ve noticed that using dried flowers produces a more stable concentrate, although less terpy.

      Thanks for your comment!

  2. James DeOrdio

    I have a full term hermaphrodite that is covered in trichomes and seed pods , can I make ice hash with this stuff ?

    1. Tim Alchimia Post author

      Hi James, thanks for the question. Yes, you can make bubble hash with this, no problem. The pollen is small enough to wash out of the mesh bags so it won’t get into the hash itself. Probably the best way to use this hermy plant, all the best, I hope it gets you some tasty hash! Happy hashing!

  3. John Francis

    Hi , great article
    Question; Do the trichomes shrivel in size when dryied

    Nice article
    Question: Do the trichomes shrivel in size when dried?
    Did you get anything in the 25 micron bad with the fresh cut ?

    Thank you

    1. Tim Alchimia Post author

      Hi John, we’re happy you’ve enjoyed the article. Thanks for your questions, yes, the trichomes shrink a little as they dry, I’ve heard it compared to a grape and a raison, although I don’t think the trichomes shrivel up anywhere near as much as raisins! And yes, with the fresh-frozen material 23% of the trichomes collected were from the 25 micron bag. I hope that clears things up for you.

      All the best

  4. Dave

    instead of assuming the weight lose being 70% why didn’t you just weight the wet sample and then weigh the dry sample?

    1. Tim Alchimia Post author

      Hi Dave, thanks for your question, it’s because we processed the “wet” (ie fresh frozen) sample while it was still wet and frozen, if we’d have dried it to weigh it, then it wouldn’t have been fresh frozen anymore! I suppose we could have retrieved the fresh frozen sample and dried it post processing but who’s got time and space for that? If you do some research you’ll see that 70-75% is a widely accepted figure for moisture loss during drying of cannabis flowers. Hope that clears up any doubt, all the best!

  5. Codygrower420

    Do you have to have a sub zero freezer to freeze Cannabis properly? Do you freeze the material right after chopping it down? Thanks

    1. Tim Alchimia Post author

      Hi Codyrower420, thanks for the question. No special freezer is required to freeze the material, although the sooner you get it frozen the better. I use a normal domestic chest freezer that gets down to -30ºC (-22ºF) if i put it on maximum, and I see no need for anything else. All the best and happy hashing!

  6. Danna Rakestraw

    Can you tell me why my hash would be so sticky that I can’t get it off the bubble bag screen? What I was able to get off the bag then stuck to the drying screen. Did it thaw during agitation causing trics to be sticky instead of frozen and snap off? Any thoughts would be appreciated. I did a test run with some larf and shake and that turned out amazing…however, when I used my fresh frozen buds the yield was almost nothing and too sticky to remove.

    1. Tim Alchimia Post author

      Hi Danna, yes I understand the issue, some varieties produce such sticky resin that it can be really challenging to work with! In these situations, cold is your friend, so you need to keep temperatures as low as possible to stop things getting too messy, often resorting to placing the bag inside the freezer to stabilise the resin and enable you to remove it from the bag. Once you’ve managed to get it out of the bag you’ll need to form it into a small patty in some parchment paper and return it to the freezer until it’s hard again. At this point you can micro-plane it (finely grate with a kitchen microplane) onto sheets pf parchment paper to dry it. With resin this sticky there’s really no other way of processing it.

      I hope that helps for future projects, all the best and happy hashing!

  7. trippn

    When running fresh frozen, I could have sworn bubbleman said it is ok to double the max capacity ( so for 20 gallon set, you can spin 2 lb of dry trim, and 4 lb fresh frozen.

    is this incorrect?

    1. Tim Alchimia Post author

      Hi trippn, thanks for the question. Effectively yes, you’re right, and that’s because fresh frozen buds will weigh up to 70% more than dry material, simply due to the water content. At the end of the day it’s the volume of the material that dictates how much you can wash at one time, not the weight. I hope that’s cleared up any doubts, all the best and happy hashing!

  8. Trevor

    This is an impressive and wonderful article. Thanks for the research.

    1. Tim Alchimia Post author

      Thanks very much, Trevor, we’re really glad you liked our work!

  9. fred fagan

    very good work, most helpful

  10. Chris

    Wish there were more articles like this, these tests are expensive! Super handy thanks.

    Do you have an opinion on whether refrigerating the bud before icolating is better than freezing it? Some say freezing breaks cell walls so you get more chlorophyll. Thanks

    1. Tim Alchimia Post author

      Hi Chris, thanks for your kind words. With regards to freezing, yes I think you’re right about the cell walls breaking and releasing more chlorophyll into the hash as the material defrosts in the washer. While many hash makers deal with this problem by keeping water temperatures very low and washing quickly to avoid defrosting, others prefer not to freeze at all. In fact, here on the blog we have an interesting post about making fresh-chilled hash that may be useful to you.

      Personally, I believe it’s very strain specific. In my experience, there are some varieties that wash really well in fresh-frozen, giving great results with no greenness at all, while others are simply impossible to get good results that way and must be washed when at least partially dried.

      I hope that’s helped, all the best and happy hashing!

  11. Chris

    Thank you Tim, that’s a great article thanks and great tips – my very limited experimentation bears out your point that it is very strain specific, although my methods aren’t always perfectly consistent and I’m often trying a few new things out (including mistakes) with each run, hence being so useful to find some proper experiments.

  12. James

    Great article guys, this was very useful to me so thank you so much for writing it. I’m about to give my first bubble hash batch a bash. Will be making it from all the heads from a pretty large tree that weren’t prime enough to dry. Sad thing is because of the season, the poor girl didn’t get any sun the last month so they’re pretty green and a little underdeveloped. I was wondering, would it be best to cut these things up nicely or do you think that’s going to have quite a large effect on the chlorophyll and plant juices that get released? I have a drop freezer where I’m keeping it for now. I’ve already sliced and diced the first half but I have another half an 8ft tree to get back to work on tomorrow. Not that I expect a reply by then! But it would be interesting to know for the next time what kind of results you’ve had from fine-cutting the buds as opposed to having them whole. I can’t imagine most of those tris will escape unless I do the chop chop… but what do I know.

    1. Tim Alchimia Post author

      Hi James, thanks for your comment and question, we’re really happy you’ve found the article helpful! When I make hash, I really like to break the buds down as much as possible (without actually grinding them up, of course). I do my best to cut each bud up into smaller florets, but being careful only to cut the stem, and not actually cut into the “meat” of the bud, which I suppose would allow more chlorophyll to be released.

      As you say, it’s the best way to get those trichomes on the interior of the flowers to easily fall off in the wash. Washing whole or large buds just won’t get you the optimal return, and you’ll have to wash more vigorously in an attempt to break the resin heads off, which in turn would probably lead to more chlorophyll in the water. With the flowers well broken up, you can wash more gently, and if you’re really diligent about keeping everything very very cold during the whole process, then chlorophyll oughtn’t to be an issue.

      Hope that helps! All the best and happy hashing!

  13. James

    Bro, all freezers are sub-zero! :’-D

  14. Jimmy D

    Hello Tim,
    Thanks for sharing the results of your work on this experiment. I was checking to see if the yields on your graphs are measured in grams? Also, any idea how much your dried buds weighed before you rehydrated them?
    Plenty regards,

    1. Tim Alchimia Post author

      Hi Jimmy, we’re glad you liked the article, thanks for the question. Yes, the measurements are all in grams and the weights given for the dried buds I washed are pre-hydration, ie. dry weight before I began washing. The complication comes when attempting to “guesstimate” the dry weight of the fresh frozen material, after much research, we settled on a 70% weight loss through the drying process. Next harvest it’d be interesting to record just how much weight is lost in water when drying the flowers. Hope that’s helped, all the best and happy hashing!

  15. Jim Wells

    Jimmy D
    June 1, 2019
    Hello Tim,
    Thanks for sharing the results of your work on this experiment. I was checking to see if the yields on your graphs are measured in grams? Also, any idea how much your dried buds weighed before you rehydrated them?

  16. Jim Wells

    Tim, thanks for the clarification. I have reread the results and have not seen where the weight of the dry buds was noted. If you could help me with this last question, I would be most appreciative. I am working on an extraction experiment as well and any information you can provide will be greatly appreciated. Regards a plenty and fresh chilled/frozen is no doubt the best way to go! Jimmy D.

    1. Tim Alchimia Post author

      Hi Jim, for this article we only published the yields by percentage, without giving any specific weights of either the starting material or the end product, I’m sorry I can’t be more help with that, if there’s anything else you need to know, just ask. All the best of luck with your experiment, please be sure to share any interesting results with use here. Happy hashing!

  17. Danny Durban

    This is a superb article with a wealth of useful information. I’d like to point out a minor language glitch only because this article is worth it: I counted 4 cases of “it’s” when it should be the possessive pronoun “its.” Perhaps you’d like to make the edits for future readers of this fine piece.

    1. Tim Alchimia Post author

      Hi Danny, thanks for your input, it really is much appreciated! I’ve made those corrections and a few more that needed changing too, hopefully it should be a much more enjoyable reading experience now! Thanks again, all the best and happy hashing.

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