Why is binding with dextrin so difficult?

[Siegmund]

Yes, been doing this off and on for ten years, but this thread feels like it belongs in the newbie section rather than the general discussion section.

 

I started out with parlon- and red-gum bound stars, ten years ago.

Even as a complete beginner, they bound perfectly, first time, every time, whether I used a bit too much solvent or a bit too little. Got me hooked on trying out a variety of star recipes as soon as I got started.

 

Now, if the forums can be believed, "everyone" binds primarily with dextrin and water, and this is supposedly a skill even novices can grasp.

 

I try it every year or two.

It doesn't save me any money over acetone - because three batches out of four go in the trash.

 

If I add too much water it turns into soup. Yup, done that.

 

If I add too little water it stays crumbly and never consolidates. Yup, done that.

 

If I get the magic sweet spot in between, perhaps it will bind normally -- or perhaps it will look wet and shiny on the outside when I press it into a patty and STILL crumble like stale bread when I cut it.

 

And then I put the dextrin back on the shelf and go back to using red gum and parlon for another year.

 

I feel like there has to be some obvious tip I am missing. Can anybody tell me what it is? I have a feeling I am not the only person who finds this a big stumbling block -- if dextrin was all there was, I'd have given the hobby up the same month I started, rather than ever getting hooked.

 

I need a little more help than "spray on a little water at a time, knead it in, and stop as soon as it clings together like putty" ... but very few comps give any clue at all (numerically) how much water to add, or if they do it's an insanely wide range.

 

Let's make this a thread a nice resource for anyone starting out with dextrin-and-water binding and help some new folks learn faster than I am

[kingkama]

Well i use my nose, dextrine have a characteristic smell when is activated, something like cookie. Usully its around 5 to 10 % of wather, as you have been told add this 5 to 10 in small increments.

[MadMat]

Are you using an alcohol/water mix when trying to bind with dextrin? If you use too much alcohol, you ruin dextrin's binding ability. I never go over 10% alcohol. Just wondering if this has been you problem all along

Edited July 4, 2020 by MadMat

[Mumbles]

Out of curiosity, what sort of dextrin are you using? Commercial is usually good, but homemade is always a little questionable and should be compared to commercial for quality, at least the first few times.

 

As for your problems:

Overwet - Not a problem. Let it dry out and cut it or process it however you see fit.

 

Appropriately wet - Should be good to go. A few extra sprays can help. Most stars don't have great wet strength, and will probably be kind of doughy. However, dextrin bound stars should still be quite a bit more robust that red gum bound stars in my experiece, which I've found to have little wet strength. Parlon bound stars I kind of hate due to the stickiness and the tail, so I don't have much experience.

 

Underwet - sounds about right. If it's crumbly, it's not suitable to patty cutting. Maybe pressing or loaf box cutting.

[Carbon796]

There are many types of dextrin, are you sure you have a yellow pyro grade ?

 

As above, you dont really need to use any alcohol for pressing or cutting stars. Some will say it helps to break suface tension. For greasy AL and lampblack type comps. But, I've never found it to be "really" necessary.

 

Dex bound comps can be crumbly as they're drying, but will become very solid once fully dry. Dex bound comps when wet for cutting, should hold together well, like putty. Not crumbly, if not, something is wrong with your dex.

 

For pressing 5% water is pretty standard for color stars. Charcoal heavy stars may like an extra percent or three. You can go up or down in percentage, to tune it to your liking. If I'm pressing, ( I use two 5 gal buckets ) I will dump all of the water in at once. Mix well with my hands then screen it 2 or 3 times through a 6 mesh. From one bucket to the other then back again. Gently pack the comp down flat into the botton of the bucket. Seal the bucket with a lid and let it temper, for at least an hour. Then re-screen it 2 or 3 times through the 6 mesh and it should be ready to press. It doesn't need to be exactly a 6 mesh 4,6,8, will probably all work, just something coarse, that will break up the comp that has more water " bound to it " when it's gently consolidated and tempering. The water will equally distribute through out the comp. And once screened again it should be very uniform in texture, if not. You can consolidate it once again, and temper some more.

 

For cutting I'll prep the comp very similarly. Add 5-7 percent water, mix, screen let temper. Break up the consolidated comp by hand, add another 5-7 percent water, mix by hand, screen, consolidate, let temper again. Once that's done I'll break up the comp, and add additional water. And fold it in by hand, till it's the right consistency for cutting. After the second tempering with additional water, the comp will respond to the additional water added for tuning very quickly. Depending on the comp, you should still be able to screen it pretty cleanly. At the 10 percent-ish water mark, with a coarse screen.

Edited July 4, 2020 by Carbon796

[Arthur]

Professional users avoid costly solvents that they would have to use by the gallon (inc fire hazard) Water is as cheap a solvent as possible it's also non flammable!

 

BUY some known good dextrin from a supplier who will ship to you, Do you have a supplier of bakery ingredients in your area they will stock it in pounds/kilos or 50 pound bags.

 

How sure are you that your stars became really dry? Dextrin comps feel soft and crumbly til they are very dry, only then do they turn into rock hard stars.

[Siegmund]

Appreciate all suggestions.

 

Yes, am using commerical dextrin (I tried to make my own and when I ran into trouble, bought a pound of commercial to eliminate that potential source of trouble.)

 

Knowing that overwet is salvageable if it's given extra time to dry out is good to know.

 

Have not been mixing alcohol and water - for red gum used denatured alcohol, for dextrin used distilled water.

 

I am always surprised at how little water I hear people are using... 5% seems to just disappear, not even wet it enough to make very many little couscous-sized balls, let alone consolidate the whole mixture. (But the amount of charcoal certainly matters - my most recent bowl of soup was caused by adding as much water to a non-charcoal star as I had to the previous (moderately successful) glitter mix.)

[Carbon796]

5% is plenty for mechanical/hydraulicly pressing most comps. It needs to be worked into the comp and thoughly distributed. Which screening and tempering help to facilitate. Tempering allows time for the binder to fully activate at your choosen moisture level. It will feel/behave dryier initially then wetter once tempered. You can use a little more or less than 5% to tune it to your taste once you get the feel for it.

 

For wetting comps to cut. I keep track of the water needed down to a half percent per comp. For example my red cuts well at 18% ( for loaf box cutting ) but I prefer 17.5% for my green. Even though they are basically the same comp. For loaf box cutting you'll generally cut with a drier comp than if your cutting patties. Those same comps will probably be closer to 23% for that operation. You just need to track your progress and take good notes. So you can have repeatable results, and eliminate guesswork. Untill you have your technique dialed in only wet out 75% of your comp. Keep 25% in reserve in case you over wet when cutting stars.

[Richtee]

Untill you have your technique dialed in only wet out 75% of your comp. Keep 25% in reserve in case you over wet when cutting stars.

 

Ya know..it took me too long to figger this out Solid advice right there.

[Arthur]

Add the minimum of water to wet the mix and leave it to stand in a sealed plastic bag for an hour or so. This helps the dampness to spread evenly through the comp.

 

If the product is very wet, it will dry! But glitters will likely be impared.

Edited July 4, 2020 by Arthur

[justvisiting]

https://www.ihaveadotcom.com/cart/index.php?main_page=product_info&cPath=72_119&products_id=283

 

Phil's General Store has the good stuff. I have yellow dextrin from another supplier that is only half as sticky. I've bought SGRS from him too, and used it for cut charcoal-based stars. I use the Ziploc Freezer bag method, and make 750-1000 gram batches. I prefer to use SGRS over dextrin, but I've made excellent cut stars and pumped comets with dextrin too. Made a few crappy batches too