Jopete's purple stars ruined by heat ?

[MinamotoKobayashi]

I made a batch of 1.5 KG of Jopete's purple stars for my next 8" double petalled shell.

The formula is:

 

0.27 Potassium perchlorate

0.27 Strontium nitrate

0.09 Copper oxide

0.10 Red gum

0.13 Parlon

0.10 Magnalium, 230-mesh

0.04 Dextrin

I rolled them around a small strobe star, perfectly dried.

As Jopetes suggest, I used 70% demineralized water and 30% ethanol.

After rolled, I spreaded all the stars over a 4 mesh sieve and putted in my ventilated dehydratator with no heat but with a fierce airflow at room temperature.

After three days the stars were perfectly dried, they do not have lost weight during the last 24 hours anymore.

The stars feel rock solid, like a stone.

The purple was a beautiful intense purple, the strobe was ... strobing!

So I have putted them inside the ventilated electric dehydratator for 2 hours at 70* to eliminate any possible residual of water.

I let them cool for some hours again in my hyper-ventilated dehydratator.

Convinced that they were as hard as steel, I took them in my hand, and to my amazement and regret I discovered that they were tender as a toffee.

The fucsia color was weakened and washed, the strobe not working anymore! But what the hell happened? How is such a thing possible?

Edited July 19, 2020 by MinamotoKobayashi

[Carbon796]

Were they a nitrate or AP based strobe ?

 

Was there any prime on them, what type ?

[MinamotoKobayashi]

Nitrate base, monocapa prime.

They was very hard before to put them in my electric dehydratator.

Now after 24 hours of intense airflow it can be easily crushed between the fingers.

It looks like a crumbly and malleable paste

Also the strobe core becomed soft. Really I do not understand what kind of reactions happened using heat.

It is the first time that I see such behaviour.

And it is the first time that I use copper oxyde with heat. It is possible that copper oxyde has reacted badly with heat?

Edited July 20, 2020 by MinamotoKobayashi

[Blackmach]

I am almost sure that your problem is due to strontium nitrate, it picks up moisture very easily. the solution is to use phenolic resin and remove the water. Good luck.

[kingkama]

Is possible that the temperature increasing solubility of strontium nitrate destroyed the stars, trontium nitrate is a bad temper guy, if you will like to use it, and have parlon why using water? Use aceton, pure or with a bit of water/alcool to reduce evaporation. Then before to use nitrate you have deidrated it?

[MinamotoKobayashi]

Yes, usually I put potassium nitrate, strontium nitrate or barium nitrate spreaded over a flat metal surface in my electric ventilated oven at 100* for one hour to remove any moisture, then I ballmill them.

I have done another batch of 15mm red stars using only alcohol 95*. I putted the stars over a 4 mesh sieve and under an intense air overflow at room temperature.

I'm monitoring every 24 hours the total weight, but fter 24 hours the stars are always soft, I do not understand why, alcohol 95* should evaporate very fast under a so strong airflow.

Probably the phenolic resin holds alcohol for longer than red gum, who knows ...

Edited July 21, 2020 by MinamotoKobayashi

[kingkama]

No I think not, the problem must to be somewhere other, same process to me produce stars solid and perfect hard in few hours, so at this point the problem can be only in the nitrate, I see you are a Precise wise guy so I don't understand. Try to not mill the nitrate but only deitrate it for few minutes, if you touch it you will understand when is dry, the milling is useless effort in color, reduce the burning time and don't make color better, when I worked in a Pyro factory we use ingredients taken directly from 25 kg bags without any other works on them if not weight and mixing. So may be that the climate in your place is damp and the milling helps to absorb the humidity from air,look also to a probability that your nitrate is full of contaminations, someway adulterated. Try for a small batch to dry nitrate 15 or 20 min mix the ingredients with a sift for two time then roll it with less alcohol you can. Let me know.

[MinamotoKobayashi]

Hi. When I receive nitrates are granulous like sugar. The first thing that every user told me is that is necessary to ballmill the powder like talcum.

In fact when I receive perch it is like talcum, not raw like the common domestic sugar.

The only thing that I changed lately is the alcohol.

The nitrates are always the same, from Pyrogarage, and never had issues.

Usually I used the classic 90* red denaturated ethilic alcohol, but with the Covid issue it is pratically impossible to found everywhere.

So I switched to 95* bio ethanol. Ethilic alcohol and ethanol is the same thing.

Bio ethanol is much better because it contain less water and do not have red colorants, it is simply transparent like water.

The term "bio" means that it is made with the fermentation of cereals or other vegetals/fruits.

It is impossible that my issue depends to this matter.

I live in a conditionating room, no umidity is present.

 

Smaller stars around 5mm diameter were dried perfectly in few hours, the red is b rilliant and dazzling, the strobe core is perfectly working also on the ground.

The biggers ones do not want to dry fast , but the 2KG batchof 15mm stars lose about 10 grams of weight every 24 hours.

Edited July 21, 2020 by MinamotoKobayashi

[kingkama]

I imagine you cannot dry them in sun, will be finer, but at the end is only a question of time, look at eventuality of some additives in ethanol, seems the one used for heating, can be inside something that reduces evaporation.

[MinamotoKobayashi]

Yes I can, I have access to a big terrance that has direct sunlight from 7 AM to 20 PM, but I heard that there are some kinds of stars that do not like direct sunlight .. perhaps the water-based stars?

Besides this, actually we have a relative humidity around 70-80%, that is no good for stars ...

 

This ethanol is very pure: no denhaturants, no colours, no chemical additives at all.

[JOPETES]

Hola minamoto. Lo primero cuando hagas estrellas redondas con nitrato de estroncio debes pulverizar y rodar con poca agua y alcohol y rodar más tiempo las estrellas para compactar mejor y que queden duras.

El primer proceso de secado que has hecho es correcto y ya no tenías humedad, solo es necesario poner las estrellas un par de horas al sol y luego guardarlas en bolsa de cierre hermético para que no absorban humedad. 70-80% de humedad relativa es muy alta.

No entiendo porqué sometes de nuevo las estrellas a 70*? Puede haber reblandecido la goma acroide y facilitar de nuevo la absorción de humedad del aire.

[MinamotoKobayashi]

Hi Jopetes, glad to hear You again!

My whole work is based on Your formulas (with exception of Winokur's stars and Dragon Eggs).

Lately I had some issue with water.

As You can read here:

 

https://www.amateurpyro.com/forums/topic/13641-dextrin-red-gum-and-phenolic-resin-replacement-and-recalculation/

 

many users suggests me to eliminate the dextrin and so the water in the whole process.

Now I created a new 2 KG batch of RED2 stars, with only phenolic resin. I have done all the recalculations to rebalance the fuel value:

 

24 Potassium perchlorate

24 Strontium nitrate

11 Strontium carbonate

10,3 Phenolic resin

12 Parlon

15 Magnalium, 230-mesh

100,3 Total

Some users has suggested me to use the electric dehydratator after drying well the stars, to eliminate completely any residual

of alcohol or water. But now the playing bells begin to be very much, it is difficult to understand where is the truth and which is the correct procedure ...

Richard.

Edited July 21, 2020 by MinamotoKobayashi

[JOPETES]

Tu resina fenolica contiene hexamina?

[JOPETES]

Sí utilizas resina fenolica en sustitución de goma acroide no seques las estrellas a 70* porque seguramente se van a reblandecer pues la resina fenolica se ablanda a temperaturas de 80-90* aunque depende del tipo de resina fenolica porque hay diferentes modelos.

[MinamotoKobayashi]

No, I do not use Hexamine. I have it but never used.

But I do not understand how a not-so-big 15mm alcohol based stars, with a strobe core already perfectly dried,

are easily crushable between the fingers 24 hours after their rolling, in a moisture-free environment,

hitted continuously by an intense air-flow generating from a big cooling-fan.

I use the phenolic resin sold by Pyrogarage, and a high quality bio-ethanol without colourants or addictives at 95*.

Smallest star around 0.5mm was perfectly dried after 24 hours, and already Monocapa-primed.

It seems only a question of time.

 

My majorn concern is: in a alcohol-based star system, a prolungated drying time can oxydize/ruin some elements

inside the stars like aluminum or magnalium, or this is an event that happens only in water-based stars?

 

And as a second important question: can I force the drying of the phenolic resin, alcohol-based stars in my electric

dehydratator at the lowest temperature available on this device set at 35°C without the softening issue?

Edited July 21, 2020 by MinamotoKobayashi

[JOPETES]

Al aluminio y magnalium no les pasa nada con mezcla de agua más alcohol o solo con alcohol sí utilizas resina fenolica.

 

Las estrellas con resina fenolica o con goma acroide no debes secar con altas temperaturas como 70*. Debes secar poco a poco a una temperatura suave como 35 o 40* está bien y luego debes guardas las estrellas secas en bolsas con cierre hermético como las que usan para congelar alimentos.

 

Si tienes mucho problema de humedad con el nitrato de estroncio no debes seguir usándolo. En el PDF tienes fórmulas de estrellas de colores muy buenos sin nitrato de estroncio y no vas a tener problemas con la humedad.

[kingkama]

As jopete said, use strontium carbonate (15%) and subs all nitrate with perchlorate, in violet you don't see a big color different, just a bit slower combustion, caused by the carbonate decomposition.

[MinamotoKobayashi]

Hello.

Actually strontium nitrate is the only element that makes me a fabulous bright red, also if the star is wetted!

I think that red is one of the most easy colour to make.

The colors that I obtain perfectly are red, purple, azure and yellow (with cryolite).

The green is pale and washed and the blue is a total disgust.

Now I will wait a few days to see how the stars lose weight.

Currently a set of 2KG loses approximately 15 grams every day.

When I see that the loss is reduced around one gram/day, I will try to put them for a few hours in my dehydrator at 35 degrees.

Thanks as always for your precious help!

[rellim]

Red 2 might work better as a pressed star since so little water is needed. Rolling with water probably produces more of the tetra hydrate. From pyro dictionary:

Strontium nitrate is normally anhydrous, but it also exists as a tetrahydrate [sr(NO3)2·4H2O], which can be obtained by recrystallization from a solution in cold water. Crystallization by evaporating the boiling solution yields the anhydrous salt. Anhydrous strontium nitrate, having a critical humidity (see humidity) of 86% relative humidity, is sufficiently hygroscopic to be of some concern when used in humid environments. Some manufacturers find it necessary to dry it in an oven and then protect it from moist air. Despite its tendency to absorb water, it can be used in some water-dampened compositions if the finished composition is well-dried.

[MinamotoKobayashi]

Thanks Rellim!

In fact I always dry it in an electric oven at 100° for 2 hours, then I ballmill it and store in a ziplog bag.

And Yes, for rolling It need much more alcohol (or water).

Now I made a new batch with only alcohol but, same problem! Easily crushable with the fingers after three days

of intense airflow in a moisture-free environment.

It seems that phenolic resin holds alcohol much longer than red gum can, especially for bigger stars.

Now I try, as Jopete suggest, to dry the stars in my electric dehydratator at 40° for some hours.

 

By the way: after a lot of days fucsia stars are rock solid, but I feel that the innermost part is again wetted because

the colour is pale and washed.

 

And now an important question: it is possible and advisable to use a mix of 50% ethanol and 50% acetone to speed

up a lot the drying time and to obtain harder stars?

Edited July 23, 2020 by MinamotoKobayashi

[Carbon796]

You could have potassium nitrate leaching, from the prime or the strobe comp,into the purple. Which will wash it out. It's a common issue that is more prominent with rolled stars. If your strobe/purple stars were not as dry as you thought. Adding a significant amount of heat while drying, could have caused a reaction, that degraded the strobe comp. Edited July 23, 2020 by Carbon796

[JOPETES]

Una mezcla de alcohol y acetona al 50% acelera bastante el tiempo de secado. hace muchos años tuve una experiencia con estrellas verdes orgánicas cuyo combustible era goma laca en lugar de goma acroide y utilicé solo alcohol para aglutinar y mi sorpresa desagradable es que nunca terminaban de secar, no podía encontrar una explicación. Pasaban los días y semanas y siempre estaban blandas las estrellas. Nunca me ha gustado aglutinar solo con alcohol.

[SharkWhisperer]

Una mezcla de alcohol y acetona al 50% acelera bastante el tiempo de secado. hace muchos años tuve una experiencia con estrellas verdes orgánicas cuyo combustible era goma laca en lugar de goma acroide y utilicé solo alcohol para aglutinar y mi sorpresa desagradable es que nunca terminaban de secar, no podía encontrar una explicación. Pasaban los días y semanas y siempre estaban blandas las estrellas. Nunca me ha gustado aglutinar solo con alcohol.

Translation:

"A mixture of alcohol and 50% acetone greatly speeds up the drying time. Many years ago I had an experience with organic green stars whose fuel was shellac instead of acrid rubber and I used only alcohol to bind and my unpleasant surprise is that they never finished drying, I couldn't find an explanation. Days and weeks passed and the stars were always soft. I have never liked to bind only with alcohol."

Edited July 24, 2020 by SharkWhisperer

[MinamotoKobayashi]

Well, after 10 days the purple stars rolled with 70% water and 30% alcohol are completely dried.

I had to put them into my electric dehydratator at 40 °C for two entire night and the rest of the time under an intense airflow

at room temperature.

The purple is an intense purple, but the strobe effect is fucked up. Probably the water together the excessive 70 °C cooking

has degraded and ruined the magnalium or created an unwanted reaction between the chems.

 

The new batch of red stars created 5 days ago with only ethanol are always soft.

It is really incredible: the stars are under intense airflow 14 hours by day in a moisture-free conditioned room, and the remaining

10 hours they are putted inside my electric dehydratator at 40 °C, and they are still soft!

A batch of 1.5KG lose only few grams by day.

At this point I fear that the main issue will be the phenolic resin.

The next batch will be rolled with a mix of 50% ethanol and 50% acetone.

If I encounter again the same issue I will switch back to red gum.

 

By the way: the red is a fantastic dazzling red despite the stars are soft and crushable between the fingers.

The strobe core is perfectly hard and the effect is not ruined. The drying temperature of 40 °C and the absence of water

probably preserve the core from degradation.

 

I haven't used Monocapa prime between the RED2 Jopete's mix and the strobe core, because the red mix alone is able

to ignite the core!

Edited July 26, 2020 by MinamotoKobayashi

[JOPETES]

Minamoto, toma algunas estrellas rojas con núcleo strobe y dejalas secar al sol haber si se secan completamente y me dices a ver qué tal.