Hygroscopic Stars

[SKC]

First attempt of star making & taste of failure.

 

On 18th of last month I tried to make some red stars with following composition.

 

SrNo3-60%

PVC-20%

MgAl-20%

AF C-3%

Dextrine-5% Solvent was water.

 

I handrolled them and primed them with classic BP.

After two days's drying in shade I kept them in an airtight container. Stars were okay till few days back until I opened the container.

When I attempted further drying in shade again they have absorbed water from atmosphere. Relative humidity is 73% where I live & weather is cloudy sometimes on these days. Yesterday I kept them under the Sun to get rid of surface moisture with success but inner core still remains soft like jelly. Today morning again it has attracted moisture on surface again. I can't make out what to do. Will these stars burn ever?

Things are not same with streamers. They have dried quite well so far.

 

[MadMat]

Your first mistake was sealing them up in a bottle before they were completely dry. There is a condition called "driven in" moisture. This is where the outside of the star dries and pretty much seals up the moisture inside the star. The slower a star dries the more likely the driven in condition will become a real problem. Sun and a breeze is very good for drying, but when you have high humidity and clouds you need a drying box. Some people have built them from scratch. I found a food dehydrator at a second hand store and it works great. The only modification I had to do was line the shelves with screening. Brand new a food dehydrator can be rather pricey, but at a resale shop, they are cheap. I got mine for $7.00

Edited June 21, 2019 by MadMat

[Arthur]

Strontium Nitrate simply IS hygroscopic. Formulae using it will be at risk of only drying in truly dry places. Strontium makes red colours BUT often the carbonate is used because that is not hygroscopic. The convenience of strontium nitrate as oxidiser and colourant is lost to the inconvenience of mixes not drying at normal atmospheric humidities comfortable for life.

[davidh]

We always store stars in paper sacks in cardboard boxes. Often empty BP boxes.

[SKC]

Thanks to all. 'Truly dry places'👍 I think I've to wait for winter.

[snapper]

build a drying box and thoroughly dry them out (1 day minimum drying time) then store in a paper bag inside a plastic bag with desiccant packs kept in a cool dry place, they are likely still salvageable but a slow low heat drying then a baggie test to see if they are done is necessary.