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Pigmenti Minerali_ BLU OLTREMARE (Naturale) -ORO BLU

Pigmenti Minerali_ BLU OLTREMARE (Naturale) -ORO BLU

Silicato di Sodio e Alluminio contenente Solfuro –  3Na2 O * 3Al2 O3 * 6SiO2 * Na2 S

Volete un pigmento che sia semi-perfetto, che si possa utilizzare indistintamente in quasi tutte le tecniche pittoriche e che sia relativamente sicuro per la salute vostra e del nostro caro pianeta?

Bene… l’azzurro oltremarino, estratto dai Lapislazzuli Afghani, fa al caso vostro, peccato che come tutte le cose belle e buone che la natura ci mette a disposizione, è  da sempre molto costoso.
Quanto costoso?… Tanto!
Basti dire che nonostante sia il pigmento più stabile e duraturo tra tutti i naturali, il problema del blu ha attanagliato dall’antichità gli artisti, che spesso non disponevano di tale importantissimo colore, proprio per via del suo costo elevato e della sua introvabilità.

Per rendersi conto della preziosità di queste pietre, basti dire che i lapislazzuli oggi, come del resto in passato, sono molti usati in gioielleria, ed essendo presente in essa inclusioni di pirite, l’hanno da sempre resa una pietra poetica riecheggiante il cielo stellato.
Sappiamo che Michelangelo ne fa un grandissimo uso nella parete dietro l’altare nella Cappella Sistina (Giudizio Universale)… ma lì pagava il Papa… e quindi…

Giotto anche utilizzò l’azzurro oltremarino negli affreschi della Cappella degli Scrovegni.
Manuali di fine XIV secolo spiegano anche i metodi di estrazione di questo prezioso pigmento dalla pietra sopra descritta.

Senza Blu non si vive, eppure anche se questo appare lapalissiano, ci è noto che il blu, era assente nelle pitture preistoriche ed antiche, dominate invece dai pigmenti rossi, neri, ocra e bruni.
La natura è ricca di coloranti blu, ma passarono secoli prima che entrarono nella tavolozza degli artisti e dei tintori, essendo difficili da individuare, estrarre ed utilizzare.
I Greci e i Romani li usavano raramente, mentre i Celti e i  Germani, ripiegarono sulla pianta del guado, per estrarre il pigmento blu, che fece nel 1300 la fortuna della città di Erfurt, che divenne cosi ricca, da poter fondare, nel 1392, un’università tra le più antiche di Europa. L’indaco, anch’esso derivante da una pianta, fu molto usato invece in Medio-Oriente.
Sinceramente non amiamo, soprattutto per la pittura muraria a fresco, pigmenti organici, il perché lo spiegheremo (forse) con un apposito articolo.

Tornando a noi, possiamo dire che in antichità il blu si ottenevano principalmente  da due minerali; azzurrite e lazurite (componente principale dei lapislazzuli).
Per fortuna la chimica dal XVIII secolo in poi ha permesso, a noi pittori che non abbiamo ancora il piacere di farci commissionare opere dal Papa in persona, che ci fa la cortesia oltre che l’onore di metterci a disposizione il pigmento puro di lapislazzuli afghani, di utilizzare dei pigmenti alternativi, economicamente più accessibili.
I Pigmenti artificiali maggiori sono derivanti dal rame: Blu di Prussia, scoperto casualmente nel 1704, il cobalto nel 1802, l’oltremare artificiale nel 1828, eccetera, fino al recentissimo blu ftalocianino nel 1934.

Da qui si apre la corsa al miglior blu sostitutivo dell’oltremarino, da utilizzare nelle differenti tecniche pittoriche, ma questo è discorso arduo, ampio e dispendioso, che ci riserviamo di ampliare alla nostra maniera nei prossimi articoli.

Nel frattempo consigliamo ai ricchi artisti, che sicuramente non avranno problemi a dipingere con l’oro blu, di non perdere tempo nella ricerca di pigmenti alternativi. L’arte contemporanea dimostra che più siete ricchi più vi vendono con facilità i rozzi ma interessati galleristi.
Dimostrate almeno di avere un briciolo di amore per coloro che acquistano inconsapevolmente le croste pagate a caro prezzo, utilizzando almeno materiali notevoli.

Anzi…no! Contrordine, non sprecate preziosi lapislazzuli, i vostri mecenati meritano la beffa più totale!

p.s: Blu di Prussia… (ammesso che lo troviate, e ammesso che non vogliate rendere felice qualche gallerista o parente poco amato in vita,  che possa sfruttare la vostra morte per rendervi doppiamente beffati nel post mortem, (s)vendendo le vostre opere al posto vostro…) evitatelo o almeno tenetelo alla larga dalla biacca, dallo zinco e dai pigmenti al cadmio, nonché dal  verde smeraldo e  il rosso venezia. E’ un pigmento velenoso, rissoso e attaccabrighe seppur diventa notevole nella realizzazione di paesaggi per ottenere verdi luminosi. Va d’accordo solo con i gialli di cromo (altro pigmento dal carattere poco raccomandabile), e con pochi altri.
Lo approfondiremo sicuramente in seguito.

Sinonimi: Bleu de Garance, Azzurro oltremarino, Azzurro di Baghdad, Cynusseythico
Inglese: Ultramarine Natural Blue
Nomi Antichi: Lazzulite, Oltra marino, Lazur, Sappheiros

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