Test of the pitch hardness

This post is meant to give information for groped to make things easier when trying to make the tool into pitch, necessary for the Bi phase and polishing parabolizzazione.
Generally, when it is explained how to make the dough for the tool, there are hardly indicated the precise percentages for ingredients, but generally they give very very generic guidelines and then it says to adjust the mixture according to 'experience (thing is usually lacking, especially if you never had the chance to get hold of a professional optical pitch, with which to get an idea of ​​reference).
If you try to search the internet for the results of the hardness of the pitch test, which are used to assess the workability at various temperatures, there are basically only results concerning specimens Gugolz or professional optics pitch and nothing regarding the various mix of rosin-bees-wax linseed oil etc., usually we use amateur scratchers here in Italy (because of difficult to find professional ones)... That's what I wanted to do tests on the samples of rosin-linseed oil mix in various amounts and mix of rosin wax-twentieth century (after I explain what) to get the most possible objective data.

PROCEDURE AND APPARATUS USED MEASURE :

The measurement procedure consisted in 'using a meter similar to the one suggested in the Stellafane site (image 1) , to carry out the measurement of the penetration of a conical steel tip with an opening angle equal to 14 ° and having the flat tip of 1 mm diametro, against a sample of pitch, when a load has been applied to 1 Kg for a period of 5 minutes.

NOTES ON MEASURING INSTRUMENTS :

The temperatures were measured with a digital thermometer with ± sensitivity 0.1 °C
The penetration measurements were made with a tool with sensitivity of ± 0.05 mm. For each sample were carried out by a minimum of 2 until 6 measurements (depending on how uncertain the results were presented), which were then averaged to obtain a more accurate. Therefore, the results presented are the result of this media.

The specimens are made:

• Mix rosin-boiled linseed oil in the percentages 3%, 6%, 9%, 12%.
• Mix rosin wax-twentieth century in the percentages 5%, 10%, 15% (the latter was then abandoned because they are already at the first measurement has proved to be too soft).

I used this wax and not that of pure bees as early realizations of tools, when I went in search of the wax in the hardware, one that I could find and I thought it could be fine is this ... which is formed mostly from pure beeswax with small percentages of other waxes all mixed with small amounts turpentine ... In the future I will try to expand the 'analysis also testing samples made with rosin-pure bees wax.

The following graph shows the results of measurements carried out ... The first in its entirety, the second by setting the maximum value of 7 mm in 'of the Y axis to "zoom" in' area of ​​most interest ... It should be noted that there are also data concerning the pitch Gugolz 64 e 55 that they have been found on the net.

They are then passed to fittare the results so as to obtain a mathematical model in the two unknowns% oil and Temperature, in order to extend the results to any percentage or desired temperature. That has been possible to realize these other 2 graphics, that they are shown in the version with penetration up to 7 mm.
The first in-Penetration Temperature Version (with the parameterized curves as a function of % linseed oil) , the second version -penetrazione% (with the parameterized curves as a function of the working temperature).

Then I looked for a relationship between the specimens with those with oil and wax since it tended to behave in a similar way ... found this report, it was possible to generate other two graphs like those above, But referring to percentages of the twentieth century wax rosin, that carryover below:

From what is indicated in various sites dedicated, the penetration range for a good mixture of pitch must be between 0.8 e 6 mm with an optimal penetration depth indicated all 'about on 2 mm. A 6 mm towards us too soft dough, while towards the 0.8 we are on dough too hard. Then of course everyone decides based on its experience and will ...

SOME CLARIFICATIONS :

1. Unfortunately, not being in possession of Gugolz pitch samples or the like can test, the data concerning them which are present in the charts, were found on the net ... they arose So even if the arrangements for the test, those results were not obtained with my tester and so it is said that the results are just compatible ( although I think that if they are not, does not much differ from each other)…
2. Please take note that the data are valid all 'inside of the temperature range in which they were made tests so they are trusted by 18.7 C have 26.3 °C, little can be said to 'outwards from these values ​​... In the future, I will try to expand the analysis also for temperatures below 18.7 °C.
3. To begin to juggle these data, the first thing you might look for a relationship between the various types of Gugolz and mixes tested. Analyzing the data we can say that the Gugolz64 tends to behave as a mixture with 9.5-10% of linseed oil or as a mixture with 8.5-9 % nine hundred wax ... While Gugolz55 seems to behave more like a mix with 7 % linseed oil or as a mixture with 6.5% nine hundred wax ..(always indicative for the reasons mentioned in points 1). P.S: Attention on the comparison of Gugolz64, because this works well at temperatures below 18.7 °C, so a better comparison you can do when you have data to lower temperatures.
4. As I said before, the dough would have to do more with the wax with oil because the wax has made me a better impression regarding the softness of the mix ... then of course every one can decide based on its experience gained and personal taste ...
5. above it was said that at various sites is indicated an optimal penetration depth around 2 mm ... in my opinion, when I tried it with the nail test samples with about 2mm penetration, It seemed a bit 'hard, then, I would suggest to stay on 3-3,5 mm as the optimal value ...

FINAL THOUGHTS :

The specimens with linseed ilio always and in any case tend to maintain a certain degree of "fragility", meaning that even in the audition with 12% Oil that is extremely "soft" where the tip down very, when I had to pull it out and moved to the right and to the left he could see that cracks were formed sull'impasto, even in depth. Then the oil is fine to soften, but it does not make the pasty mix.
As for the wax instead I have to say I made a good impression, He manages to soften the mix but also making it less brittle and pasty.
A good compromise would be to use both of them in the mix that you have to prepare maybe in percentages 50-50, giving more emphasis a bit 'more about the wax if you must choose between one or the other ...

The work is very useful especially to have a pretty good idea of ​​the maximum quantities to be used already in the first instance ... .Voglio it points out that in any case it is a job done by me, without any claim to be a job with precision laboratory, therefore it should be used with due care.